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Schedule III - Real Estate and Accumulated Depreciation (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Real Estate and Accumulated Depreciation [Line Items]        
Encumbrances $ 599,985us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances      
Initial Cost of Land 743,319us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand      
Building and Improvements 1,635,277us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements      
Costs capitalized subsequent to acquisition or completion and valuation provision 779,479us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements      
Land 718,188us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand      
Building and improvements 2,439,887us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements      
Total 3,158,075us-gaap_RealEstateGrossAtCarryingValue      
Accumulated depreciation 12/31/2012 786,978us-gaap_RealEstateAccumulatedDepreciation 748,044us-gaap_RealEstateAccumulatedDepreciation 735,593us-gaap_RealEstateAccumulatedDepreciation 695,931us-gaap_RealEstateAccumulatedDepreciation
4250 River Green Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Duluth, GA      
Initial Cost of Land 264us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveZeroRiverGreenParkwayMember
     
Building and Improvements 1,522us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveZeroRiverGreenParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 82us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveZeroRiverGreenParkwayMember
     
Land 214us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveZeroRiverGreenParkwayMember
     
Building and improvements 1,654us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveZeroRiverGreenParkwayMember
     
Total 1,868us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveZeroRiverGreenParkwayMember
     
Accumulated depreciation 12/31/2012 871us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveZeroRiverGreenParkwayMember
     
1650 Highway 155 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) McDonough, GA      
Initial Cost of Land 788us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixFiveZeroHighwayOneFiveFiveMember
     
Building and Improvements 4,544us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixFiveZeroHighwayOneFiveFiveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (363)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixFiveZeroHighwayOneFiveFiveMember
     
Land 365us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixFiveZeroHighwayOneFiveFiveMember
     
Building and improvements 4,604us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixFiveZeroHighwayOneFiveFiveMember
     
Total 4,969us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixFiveZeroHighwayOneFiveFiveMember
     
Accumulated depreciation 12/31/2012 2,602us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixFiveZeroHighwayOneFiveFiveMember
     
1665 Dogwood [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Conyers, GA      
Initial Cost of Land 635us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixFiveDogwoodDriveMember
     
Building and Improvements 3,662us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixFiveDogwoodDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 972us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixFiveDogwoodDriveMember
     
Land 635us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixFiveDogwoodDriveMember
     
Building and improvements 4,634us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixFiveDogwoodDriveMember
     
Total 5,269us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixFiveDogwoodDriveMember
     
Accumulated depreciation 12/31/2012 2,230us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixFiveDogwoodDriveMember
     
1715 Dogwood [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Conyers, GA      
Initial Cost of Land 288us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenOneFiveDogwoodMember
     
Building and Improvements 1,675us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenOneFiveDogwoodMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 827us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenOneFiveDogwoodMember
     
Land 228us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenOneFiveDogwoodMember
     
Building and improvements 2,562us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenOneFiveDogwoodMember
     
Total 2,790us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenOneFiveDogwoodMember
     
Accumulated depreciation 12/31/2012 1,052us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenOneFiveDogwoodMember
     
11235 Harland Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Covington, GA      
Initial Cost of Land 125us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneTwoThreeFiveHarlandDriveMember
     
Building and Improvements 739us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneTwoThreeFiveHarlandDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 218us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneTwoThreeFiveHarlandDriveMember
     
Land 125us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneTwoThreeFiveHarlandDriveMember
     
Building and improvements 957us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneTwoThreeFiveHarlandDriveMember
     
Total 1,082us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneTwoThreeFiveHarlandDriveMember
     
Accumulated depreciation 12/31/2012 433us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneTwoThreeFiveHarlandDriveMember
     
4051 Southmeadow Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Atlanta, GA      
Initial Cost of Land 726us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveOneSouthmeadowParkwayMember
     
Building and Improvements 4,130us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveOneSouthmeadowParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 880us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveOneSouthmeadowParkwayMember
     
Land 726us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveOneSouthmeadowParkwayMember
     
Building and improvements 5,010us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveOneSouthmeadowParkwayMember
     
Total 5,736us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveOneSouthmeadowParkwayMember
     
Accumulated depreciation 12/31/2012 2,366us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveOneSouthmeadowParkwayMember
     
4071 Southmeadow Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Atlanta, GA      
Initial Cost of Land 750us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroSevenOneSouthmeadowParkwayMember
     
Building and Improvements 4,460us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroSevenOneSouthmeadowParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,742us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroSevenOneSouthmeadowParkwayMember
     
Land 828us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroSevenOneSouthmeadowParkwayMember
     
Building and improvements 6,124us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroSevenOneSouthmeadowParkwayMember
     
Total 6,952us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroSevenOneSouthmeadowParkwayMember
     
Accumulated depreciation 12/31/2012 2,919us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroSevenOneSouthmeadowParkwayMember
     
4081 Southmeadow Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Atlanta, GA      
Initial Cost of Land 1,012us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroEightOneSouthmeadowParkwayMember
     
Building and Improvements 5,918us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroEightOneSouthmeadowParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,796us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroEightOneSouthmeadowParkwayMember
     
Land 1,157us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroEightOneSouthmeadowParkwayMember
     
Building and improvements 7,569us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroEightOneSouthmeadowParkwayMember
     
Total 8,726us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroEightOneSouthmeadowParkwayMember
     
Accumulated depreciation 12/31/2012 3,409us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroEightOneSouthmeadowParkwayMember
     
5570 Tulane Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Atlanta, GA      
Encumbrances 2,218us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
Initial Cost of Land 527us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
Building and Improvements 2,984us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,184us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
Land 546us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
Building and improvements 4,149us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
Total 4,695us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
Accumulated depreciation 12/31/2012 1,694us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveSevenZeroTulaneDriveDMember
     
955 Cobb Place [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Kennesaw, GA      
Encumbrances 2,895us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
Initial Cost of Land 780us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
Building and Improvements 4,420us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 927us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
Land 804us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
Building and improvements 5,323us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
Total 6,127us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
Accumulated depreciation 12/31/2012 2,100us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveFiveCobbPlaceMember
     
1005 Sigman Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Conyers, GA      
Encumbrances 2,127us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
Initial Cost of Land 566us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
Building and Improvements 3,134us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 433us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
Land 574us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
Building and improvements 3,559us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
Total 4,133us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
Accumulated depreciation 12/31/2012 1,318us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroFiveSigmanRoadMember
     
2050 East Park Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Conyers, GA      
Initial Cost of Land 452us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroFiveZeroEastParkDriveMember
     
Building and Improvements 2,504us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroFiveZeroEastParkDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 151us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroFiveZeroEastParkDriveMember
     
Land 459us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroFiveZeroEastParkDriveMember
     
Building and improvements 2,648us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroFiveZeroEastParkDriveMember
     
Total 3,107us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroFiveZeroEastParkDriveMember
     
Accumulated depreciation 12/31/2012 998us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroFiveZeroEastParkDriveMember
     
1256 Oakbrook Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 336us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveSixOakbrookDriveMember
     
Building and Improvements 1,907us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveSixOakbrookDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 340us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveSixOakbrookDriveMember
     
Land 339us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveSixOakbrookDriveMember
     
Building and improvements 2,244us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveSixOakbrookDriveMember
     
Total 2,583us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveSixOakbrookDriveMember
     
Accumulated depreciation 12/31/2012 744us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveSixOakbrookDriveMember
     
1265 Oakbrook Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 307us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixFiveOakbrookDriveMember
     
Building and Improvements 1,742us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixFiveOakbrookDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 335us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixFiveOakbrookDriveMember
     
Land 309us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixFiveOakbrookDriveMember
     
Building and improvements 2,075us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixFiveOakbrookDriveMember
     
Total 2,384us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixFiveOakbrookDriveMember
     
Accumulated depreciation 12/31/2012 698us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixFiveOakbrookDriveMember
     
1280 Oakbrook Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 281us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroOakbrookDriveMember
     
Building and Improvements 1,592us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroOakbrookDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 286us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroOakbrookDriveMember
     
Land 283us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroOakbrookDriveMember
     
Building and improvements 1,876us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroOakbrookDriveMember
     
Total 2,159us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroOakbrookDriveMember
     
Accumulated depreciation 12/31/2012 624us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroOakbrookDriveMember
     
1300 Oakbrook Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 420us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroZeroOakbrookDriveMember
     
Building and Improvements 2,381us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroZeroOakbrookDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 254us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroZeroOakbrookDriveMember
     
Land 423us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroZeroOakbrookDriveMember
     
Building and improvements 2,632us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroZeroOakbrookDriveMember
     
Total 3,055us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroZeroOakbrookDriveMember
     
Accumulated depreciation 12/31/2012 866us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroZeroOakbrookDriveMember
     
1325 Oakbrook Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 332us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoFiveOakbrookDriveMember
     
Building and Improvements 1,879us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoFiveOakbrookDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 338us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoFiveOakbrookDriveMember
     
Land 334us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoFiveOakbrookDriveMember
     
Building and improvements 2,215us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoFiveOakbrookDriveMember
     
Total 2,549us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoFiveOakbrookDriveMember
     
Accumulated depreciation 12/31/2012 743us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoFiveOakbrookDriveMember
     
1351 Oakbrook Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 370us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveOneOakbrookDriveMember
     
Building and Improvements 2,099us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveOneOakbrookDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,020)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveOneOakbrookDriveMember
     
Land 146us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveOneOakbrookDriveMember
     
Building and improvements 1,303us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveOneOakbrookDriveMember
     
Total 1,449us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveOneOakbrookDriveMember
     
Accumulated depreciation 12/31/2012 626us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveOneOakbrookDriveMember
     
1346 Oakbrook Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 740us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourSixOakbrookDriveMember
     
Building and Improvements 4,192us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourSixOakbrookDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (684)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourSixOakbrookDriveMember
     
Land 352us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourSixOakbrookDriveMember
     
Building and improvements 3,896us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourSixOakbrookDriveMember
     
Total 4,248us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourSixOakbrookDriveMember
     
Accumulated depreciation 12/31/2012 1,925us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourSixOakbrookDriveMember
     
3060 South Park Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ellenwood, GA      
Initial Cost of Land 1,600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroSouthParkBlvdMember
     
Building and Improvements 12,464us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroSouthParkBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,691us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroSouthParkBlvdMember
     
Land 1,604us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroSouthParkBlvdMember
     
Building and improvements 15,151us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroSouthParkBlvdMember
     
Total 16,755us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroSouthParkBlvdMember
     
Accumulated depreciation 12/31/2012 4,306us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroSouthParkBlvdMember
     
Greenwood Industrial Park [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) McDonough, GA      
Encumbrances 4,338us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_GreenwoodIndustrialParkMember
     
Initial Cost of Land 1,550us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_GreenwoodIndustrialParkMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 7,632us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_GreenwoodIndustrialParkMember
     
Land 1,550us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_GreenwoodIndustrialParkMember
     
Building and improvements 7,632us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_GreenwoodIndustrialParkMember
     
Total 9,182us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_GreenwoodIndustrialParkMember
     
Accumulated depreciation 12/31/2012 1,943us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_GreenwoodIndustrialParkMember
     
46 Kent Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Cartersville GA      
Encumbrances 1,415us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
Initial Cost of Land 794us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
Building and Improvements 2,252us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (52)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
Land 798us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
Building and improvements 2,196us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
Total 2,994us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
Accumulated depreciation 12/31/2012 770us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixKentDriveMember
     
605 Stonehill Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Atlanta, GA      
Initial Cost of Land 485us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroFiveStonehillDriveMember
     
Building and Improvements 1,979us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroFiveStonehillDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (23)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroFiveStonehillDriveMember
     
Land 490us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroFiveStonehillDriveMember
     
Building and improvements 1,951us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroFiveStonehillDriveMember
     
Total 2,441us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroFiveStonehillDriveMember
     
Accumulated depreciation 12/31/2012 1,704us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroFiveStonehillDriveMember
     
5095 Phillip Lee Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Atlanta, GA      
Encumbrances 4,885us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
Initial Cost of Land 735us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
Building and Improvements 3,627us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 485us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
Land 740us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
Building and improvements 4,107us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
Total 4,847us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
Accumulated depreciation 12/31/2012 2,358us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroNineFivePhillipLeeDriveMember
     
6514 Warren Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 510us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveOneFourWarrenDriveMember
     
Building and Improvements 1,250us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveOneFourWarrenDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 127us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveOneFourWarrenDriveMember
     
Land 513us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveOneFourWarrenDriveMember
     
Building and improvements 1,374us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveOneFourWarrenDriveMember
     
Total 1,887us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveOneFourWarrenDriveMember
     
Accumulated depreciation 12/31/2012 454us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveOneFourWarrenDriveMember
     
6544 Warren Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norcross, GA      
Initial Cost of Land 711us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourFourWarrenDriveMember
     
Building and Improvements 2,310us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourFourWarrenDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 293us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourFourWarrenDriveMember
     
Land 715us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourFourWarrenDriveMember
     
Building and improvements 2,599us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourFourWarrenDriveMember
     
Total 3,314us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourFourWarrenDriveMember
     
Accumulated depreciation 12/31/2012 906us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourFourWarrenDriveMember
     
5356 E. Ponce De Leon [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Stone Mountain, GA      
Initial Cost of Land 604us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveSixEPonceDeLeonMember
     
Building and Improvements 3,888us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveSixEPonceDeLeonMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 90us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveSixEPonceDeLeonMember
     
Land 610us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveSixEPonceDeLeonMember
     
Building and improvements 3,972us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveSixEPonceDeLeonMember
     
Total 4,582us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveSixEPonceDeLeonMember
     
Accumulated depreciation 12/31/2012 1,811us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveSixEPonceDeLeonMember
     
5390 E. Ponce De Leon [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Stone Mountain, GA      
Initial Cost of Land 397us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineZeroEPonceDeLeonMember
     
Building and Improvements 1,791us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineZeroEPonceDeLeonMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 108us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineZeroEPonceDeLeonMember
     
Land 402us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineZeroEPonceDeLeonMember
     
Building and improvements 1,894us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineZeroEPonceDeLeonMember
     
Total 2,296us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineZeroEPonceDeLeonMember
     
Accumulated depreciation 12/31/2012 705us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineZeroEPonceDeLeonMember
     
195 & 197 Collins Boulevard [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Athens, GA      
Initial Cost of Land 1,410us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFiveAndOneNineSevenCollinsBoulevardMember
     
Building and Improvements 5,344us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFiveAndOneNineSevenCollinsBoulevardMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 896us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFiveAndOneNineSevenCollinsBoulevardMember
     
Land 989us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFiveAndOneNineSevenCollinsBoulevardMember
     
Building and improvements 6,661us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFiveAndOneNineSevenCollinsBoulevardMember
     
Total 7,650us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFiveAndOneNineSevenCollinsBoulevardMember
     
Accumulated depreciation 12/31/2012 3,516us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFiveAndOneNineSevenCollinsBoulevardMember
     
1755 Enterprise Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Buford, GA      
Encumbrances 1,242us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
Initial Cost of Land 712us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
Building and Improvements 2,118us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (202)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
Land 716us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
Building and improvements 1,912us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
Total 2,628us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
Accumulated depreciation 12/31/2012 618us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFiveFiveEnterpriseDriveMember
     
4555 Atwater Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Buford, GA      
Encumbrances 2,235us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
Initial Cost of Land 881us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
Building and Improvements 3,550us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 298us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
Land 885us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
Building and improvements 3,844us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
Total 4,729us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
Accumulated depreciation 12/31/2012 1,048us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveFiveFiveAtwaterCourtMember
     
80 Liberty Industrial Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) McDonough, GA      
Initial Cost of Land 756us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroLibertyIndustrialParkwayMember
     
Building and Improvements 3,695us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroLibertyIndustrialParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,244)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroLibertyIndustrialParkwayMember
     
Land 467us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroLibertyIndustrialParkwayMember
     
Building and improvements 2,740us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroLibertyIndustrialParkwayMember
     
Total 3,207us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroLibertyIndustrialParkwayMember
     
Accumulated depreciation 12/31/2012 902us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroLibertyIndustrialParkwayMember
     
596 Bonnie Valentine [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pendergrass, GA      
Initial Cost of Land 2,580us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSixBonnieValentineMember
     
Building and Improvements 21,730us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSixBonnieValentineMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,675us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSixBonnieValentineMember
     
Land 2,594us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSixBonnieValentineMember
     
Building and improvements 25,391us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSixBonnieValentineMember
     
Total 27,985us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSixBonnieValentineMember
     
Accumulated depreciation 12/31/2012 5,939us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSixBonnieValentineMember
     
11415 Old Roswell Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Alpharetta, GA      
Encumbrances 3,126us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
Initial Cost of Land 2,403us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
Building and Improvements 1,912us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 628us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
Land 2,428us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
Building and improvements 2,515us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
Total 4,943us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
Accumulated depreciation 12/31/2012 963us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourOneFiveOldRoswellRoadMember
     
9700 Martin Luther King Hwy [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 700us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredMartinLutherKingHwyMember
     
Building and Improvements 1,920us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredMartinLutherKingHwyMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 742us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredMartinLutherKingHwyMember
     
Land 700us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredMartinLutherKingHwyMember
     
Building and improvements 2,662us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredMartinLutherKingHwyMember
     
Total 3,362us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredMartinLutherKingHwyMember
     
Accumulated depreciation 12/31/2012 1,103us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredMartinLutherKingHwyMember
     
9730 Martin Luther King Hwy [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 500us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredThirtyMartinLutherKingHwyMember
     
Building and Improvements 955us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredThirtyMartinLutherKingHwyMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 535us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredThirtyMartinLutherKingHwyMember
     
Land 500us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredThirtyMartinLutherKingHwyMember
     
Building and improvements 1,490us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredThirtyMartinLutherKingHwyMember
     
Total 1,990us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredThirtyMartinLutherKingHwyMember
     
Accumulated depreciation 12/31/2012 581us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredThirtyMartinLutherKingHwyMember
     
4621 Boston Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 1,100us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredTwentyOneBostonWayMember
     
Building and Improvements 3,070us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredTwentyOneBostonWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 517us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredTwentyOneBostonWayMember
     
Land 1,100us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredTwentyOneBostonWayMember
     
Building and improvements 3,587us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredTwentyOneBostonWayMember
     
Total 4,687us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredTwentyOneBostonWayMember
     
Accumulated depreciation 12/31/2012 1,338us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredTwentyOneBostonWayMember
     
4720 Boston Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 1,200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTwentyBostonWayMember
     
Building and Improvements 2,174us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTwentyBostonWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 792us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTwentyBostonWayMember
     
Land 1,200us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTwentyBostonWayMember
     
Building and improvements 2,966us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTwentyBostonWayMember
     
Total 4,166us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTwentyBostonWayMember
     
Accumulated depreciation 12/31/2012 1,047us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTwentyBostonWayMember
     
22520 Randolph Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dulles, VA      
Initial Cost of Land 3,200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandFiveHundredTwentyRandolphDriveDullesMember
     
Building and Improvements 8,187us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandFiveHundredTwentyRandolphDriveDullesMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (656)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandFiveHundredTwentyRandolphDriveDullesMember
     
Land 3,208us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandFiveHundredTwentyRandolphDriveDullesMember
     
Building and improvements 7,523us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandFiveHundredTwentyRandolphDriveDullesMember
     
Total 10,731us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandFiveHundredTwentyRandolphDriveDullesMember
     
Accumulated depreciation 12/31/2012 1,675us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandFiveHundredTwentyRandolphDriveDullesMember
     
22630 Dulles Summit Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dulles, VA      
Initial Cost of Land 2,200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandSixHundredThirtyDullesSummitCourtMember
     
Building and Improvements 9,346us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandSixHundredThirtyDullesSummitCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (820)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandSixHundredThirtyDullesSummitCourtMember
     
Land 2,206us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandSixHundredThirtyDullesSummitCourtMember
     
Building and improvements 8,520us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandSixHundredThirtyDullesSummitCourtMember
     
Total 10,726us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandSixHundredThirtyDullesSummitCourtMember
     
Accumulated depreciation 12/31/2012 1,994us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyTwoThousandSixHundredThirtyDullesSummitCourtMember
     
4201 Forbes Boulevard [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 356us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandTwoHundredOneForbesBoulevardMember
     
Building and Improvements 1,823us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandTwoHundredOneForbesBoulevardMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 186us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandTwoHundredOneForbesBoulevardMember
     
Land 375us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandTwoHundredOneForbesBoulevardMember
     
Building and improvements 1,990us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandTwoHundredOneForbesBoulevardMember
     
Total 2,365us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandTwoHundredOneForbesBoulevardMember
     
Accumulated depreciation 12/31/2012 586us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandTwoHundredOneForbesBoulevardMember
     
4370-4383 Lottsford Vista Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 279us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandThreeHundredSeventyAndFourThousandThreeHundredEightyThreeLottsfordVistaRdMember
     
Building and Improvements 1,358us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandThreeHundredSeventyAndFourThousandThreeHundredEightyThreeLottsfordVistaRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 89us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandThreeHundredSeventyAndFourThousandThreeHundredEightyThreeLottsfordVistaRdMember
     
Land 296us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandThreeHundredSeventyAndFourThousandThreeHundredEightyThreeLottsfordVistaRdMember
     
Building and improvements 1,430us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandThreeHundredSeventyAndFourThousandThreeHundredEightyThreeLottsfordVistaRdMember
     
Total 1,726us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandThreeHundredSeventyAndFourThousandThreeHundredEightyThreeLottsfordVistaRdMember
     
Accumulated depreciation 12/31/2012 325us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandThreeHundredSeventyAndFourThousandThreeHundredEightyThreeLottsfordVistaRdMember
     
4400 Lottsford Vista Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 351us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredLottsfordVistaRdMember
     
Building and Improvements 1,955us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredLottsfordVistaRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 241us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredLottsfordVistaRdMember
     
Land 372us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredLottsfordVistaRdMember
     
Building and improvements 2,175us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredLottsfordVistaRdMember
     
Total 2,547us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredLottsfordVistaRdMember
     
Accumulated depreciation 12/31/2012 581us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredLottsfordVistaRdMember
     
4420 Lottsford Vista Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lanham, MD      
Initial Cost of Land 539us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredTwentyLottsfordVistaRoadMember
     
Building and Improvements 2,196us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredTwentyLottsfordVistaRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 6us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredTwentyLottsfordVistaRoadMember
     
Land 568us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredTwentyLottsfordVistaRoadMember
     
Building and improvements 2,173us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredTwentyLottsfordVistaRoadMember
     
Total 2,741us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredTwentyLottsfordVistaRoadMember
     
Accumulated depreciation 12/31/2012 587us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredTwentyLottsfordVistaRoadMember
     
11204 McCormick Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hunt Valley, MD      
Initial Cost of Land 1,017us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFourMcCormickRoadMember
     
Building and Improvements 3,132us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFourMcCormickRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (59)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFourMcCormickRoadMember
     
Land 1,038us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFourMcCormickRoadMember
     
Building and improvements 3,052us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFourMcCormickRoadMember
     
Total 4,090us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFourMcCormickRoadMember
     
Accumulated depreciation 12/31/2012 1,184us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFourMcCormickRoadMember
     
11110 Pepper Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hunt Valley, MD      
Initial Cost of Land 918us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredTenPepperRoadMember
     
Building and Improvements 2,529us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredTenPepperRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 281us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredTenPepperRoadMember
     
Land 938us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredTenPepperRoadMember
     
Building and improvements 2,790us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredTenPepperRoadMember
     
Total 3,728us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredTenPepperRoadMember
     
Accumulated depreciation 12/31/2012 1,012us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredTenPepperRoadMember
     
11100-11120 Gilroy Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hunt Valley, MD      
Initial Cost of Land 901us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredAndElevenThousandOneHundredTwentyGilroyRoadMember
     
Building and Improvements 1,455us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredAndElevenThousandOneHundredTwentyGilroyRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 166us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredAndElevenThousandOneHundredTwentyGilroyRoadMember
     
Land 919us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredAndElevenThousandOneHundredTwentyGilroyRoadMember
     
Building and improvements 1,603us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredAndElevenThousandOneHundredTwentyGilroyRoadMember
     
Total 2,522us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredAndElevenThousandOneHundredTwentyGilroyRoadMember
     
Accumulated depreciation 12/31/2012 569us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandOneHundredAndElevenThousandOneHundredTwentyGilroyRoadMember
     
318 Clubhouse Lane [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hunt Valley, MD      
Initial Cost of Land 701us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredEighteenClubhouseLaneMember
     
Building and Improvements 1,691us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredEighteenClubhouseLaneMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (106)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredEighteenClubhouseLaneMember
     
Land 718us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredEighteenClubhouseLaneMember
     
Building and improvements 1,568us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredEighteenClubhouseLaneMember
     
Total 2,286us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredEighteenClubhouseLaneMember
     
Accumulated depreciation 12/31/2012 532us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredEighteenClubhouseLaneMember
     
10709 Gilroy Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hunt Valley, MD      
Encumbrances 2,348us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
Initial Cost of Land 913us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
Building and Improvements 2,705us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (143)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
Land 913us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
Building and improvements 2,562us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
Total 3,475us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
Accumulated depreciation 12/31/2012 1,172us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredNineGilroyRoadMember
     
10707 Gilroy Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hunt Valley, MD      
Initial Cost of Land 1,111us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredSevenGilroyRoadMember
     
Building and Improvements 3,819us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredSevenGilroyRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 502us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredSevenGilroyRoadMember
     
Land 1,136us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredSevenGilroyRoadMember
     
Building and improvements 4,296us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredSevenGilroyRoadMember
     
Total 5,432us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredSevenGilroyRoadMember
     
Accumulated depreciation 12/31/2012 1,491us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandSevenHundredSevenGilroyRoadMember
     
38 Loveton Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Sparks, MD      
Initial Cost of Land 1,648us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirtyEightLovetonCircleMember
     
Building and Improvements 2,151us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirtyEightLovetonCircleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (241)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirtyEightLovetonCircleMember
     
Land 1,690us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirtyEightLovetonCircleMember
     
Building and improvements 1,868us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirtyEightLovetonCircleMember
     
Total 3,558us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirtyEightLovetonCircleMember
     
Accumulated depreciation 12/31/2012 722us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirtyEightLovetonCircleMember
     
1225 Bengies Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Baltimore, MD      
Initial Cost of Land 2,640us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredTwentyFiveBengiesRoadMember
     
Building and Improvements 270us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredTwentyFiveBengiesRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 14,041us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredTwentyFiveBengiesRoadMember
     
Land 2,823us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredTwentyFiveBengiesRoadMember
     
Building and improvements 14,128us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredTwentyFiveBengiesRoadMember
     
Total 16,951us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredTwentyFiveBengiesRoadMember
     
Accumulated depreciation 12/31/2012 3,352us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredTwentyFiveBengiesRoadMember
     
1214-B Freedom Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Cranberry Township, PA      
Encumbrances 1,359us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
Initial Cost of Land 31us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
Building and Improvements 994us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 613us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
Land 200us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
Building and improvements 1,438us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
Total 1,638us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
Accumulated depreciation 12/31/2012 1,191us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwoHundredAndFourteenBFreedomRoadMember
     
401 Russell Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Middletown, PA      
Initial Cost of Land 262us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneRussellDriveMember
     
Building and Improvements 857us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneRussellDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,696us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneRussellDriveMember
     
Land 287us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneRussellDriveMember
     
Building and improvements 2,528us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneRussellDriveMember
     
Total 2,815us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneRussellDriveMember
     
Accumulated depreciation 12/31/2012 1,891us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneRussellDriveMember
     
2700 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Middletown, PA      
Initial Cost of Land 196us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredCommerceDriveMember
     
Building and Improvements 997us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 935us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredCommerceDriveMember
     
Land 206us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredCommerceDriveMember
     
Building and improvements 1,922us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredCommerceDriveMember
     
Total 2,128us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredCommerceDriveMember
     
Accumulated depreciation 12/31/2012 1,421us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredCommerceDriveMember
     
2701 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Middletown, PA      
Encumbrances 1,884us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
Initial Cost of Land 141us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
Building and Improvements 859us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,270us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
Land 164us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
Building and improvements 2,106us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
Total 2,270us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
Accumulated depreciation 12/31/2012 1,403us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndOneCommerceDriveMember
     
2780 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Middletown, PA      
Encumbrances 1,648us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
Initial Cost of Land 113us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
Building and Improvements 743us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,130us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
Land 209us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
Building and improvements 1,777us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
Total 1,986us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
Accumulated depreciation 12/31/2012 1,349us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandSevenHundredAndEightyCommerceDriveMember
     
350 Old Silver Spring Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Mechanicsburg, PA      
Initial Cost of Land 510us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredAndFiftyOldSilverSpringRoadMember
     
Building and Improvements 2,890us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredAndFiftyOldSilverSpringRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 7,043us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredAndFiftyOldSilverSpringRoadMember
     
Land 541us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredAndFiftyOldSilverSpringRoadMember
     
Building and improvements 9,902us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredAndFiftyOldSilverSpringRoadMember
     
Total 10,443us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredAndFiftyOldSilverSpringRoadMember
     
Accumulated depreciation 12/31/2012 3,975us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredAndFiftyOldSilverSpringRoadMember
     
16522 Hunters Green Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hagerstown, MD      
Encumbrances 12,222us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
Initial Cost of Land 1,390us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
Building and Improvements 13,104us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 4,841us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
Land 1,863us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
Building and improvements 17,472us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
Total 19,335us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
Accumulated depreciation 12/31/2012 4,732us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandAndFiveHundredAndTwentyTwoHuntersGreenParkwayMember
     
18212 Shawley Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hagerstown, MD      
Encumbrances 6,438us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
Initial Cost of Land 1,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
Building and Improvements 5,847us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 910us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
Land 1,016us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
Building and improvements 6,741us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
Total 7,757us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
Accumulated depreciation 12/31/2012 1,683us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandTwoHundredAndTwelveShawleyDriveMember
     
37 Valley View Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Jessup, PA      
Encumbrances 2,954us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenValleyViewDriveMember
     
Initial Cost of Land 542us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenValleyViewDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,017us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenValleyViewDriveMember
     
Land 532us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenValleyViewDriveMember
     
Building and improvements 3,027us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenValleyViewDriveMember
     
Total 3,559us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenValleyViewDriveMember
     
Accumulated depreciation 12/31/2012 752us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenValleyViewDriveMember
     
301 Railroad Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shiremanstown, PA      
Initial Cost of Land 1,181us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredOneRailroadAvenueMember
     
Building and Improvements 4,447us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredOneRailroadAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,034us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredOneRailroadAvenueMember
     
Land 1,328us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredOneRailroadAvenueMember
     
Building and improvements 7,334us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredOneRailroadAvenueMember
     
Total 8,662us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredOneRailroadAvenueMember
     
Accumulated depreciation 12/31/2012 3,078us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredOneRailroadAvenueMember
     
431 Railroad Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shiremanstown, PA      
Encumbrances 8,297us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
Initial Cost of Land 1,293us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
Building and Improvements 7,164us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,666us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
Land 1,341us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
Building and improvements 8,782us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
Total 10,123us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
Accumulated depreciation 12/31/2012 3,518us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThirtyOneRailroadAvenueMember
     
6951 Allentown Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Harrisburg, PA      
Initial Cost of Land 585us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandNineHundredAndFiftyOneAllentownBlvdMember
     
Building and Improvements 3,176us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandNineHundredAndFiftyOneAllentownBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 301us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandNineHundredAndFiftyOneAllentownBlvdMember
     
Land 601us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandNineHundredAndFiftyOneAllentownBlvdMember
     
Building and improvements 3,461us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandNineHundredAndFiftyOneAllentownBlvdMember
     
Total 4,062us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandNineHundredAndFiftyOneAllentownBlvdMember
     
Accumulated depreciation 12/31/2012 1,181us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandNineHundredAndFiftyOneAllentownBlvdMember
     
320 Reliance Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Washington, PA      
Initial Cost of Land 201us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroRelianceRoadMember
     
Building and Improvements 1,819us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroRelianceRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (282)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroRelianceRoadMember
     
Land 178us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroRelianceRoadMember
     
Building and improvements 1,560us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroRelianceRoadMember
     
Total 1,738us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroRelianceRoadMember
     
Accumulated depreciation 12/31/2012 734us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroRelianceRoadMember
     
1351 Eisenhower Blvd., Bldg 1 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Harrisburg, PA      
Initial Cost of Land 382us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgOneMember
     
Building and Improvements 2,343us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgOneMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (64)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgOneMember
     
Land 387us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgOneMember
     
Building and improvements 2,274us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgOneMember
     
Total 2,661us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgOneMember
     
Accumulated depreciation 12/31/2012 721us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgOneMember
     
1351 Eisenhower Blvd., Bldg 2 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Harrisburg, PA      
Initial Cost of Land 436us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgTwoMember
     
Building and Improvements 1,587us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgTwoMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 43us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgTwoMember
     
Land 443us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgTwoMember
     
Building and improvements 1,623us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgTwoMember
     
Total 2,066us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgTwoMember
     
Accumulated depreciation 12/31/2012 601us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandThreeHundredAndFiftyOneEisenhowerBlvdBldgTwoMember
     
1490 Dennison Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlisle, PA      
Initial Cost of Land 1,500us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredNinetyDennisonCircleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 13,880us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredNinetyDennisonCircleMember
     
Land 2,341us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredNinetyDennisonCircleMember
     
Building and improvements 13,039us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredNinetyDennisonCircleMember
     
Total 15,380us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredNinetyDennisonCircleMember
     
Accumulated depreciation 12/31/2012 2,722us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredNinetyDennisonCircleMember
     
298 First Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Gouldsboro, PA      
Initial Cost of Land 7,022us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineEightFirstAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 57,272us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineEightFirstAvenueMember
     
Land 7,019us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineEightFirstAvenueMember
     
Building and improvements 57,275us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineEightFirstAvenueMember
     
Total 64,294us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineEightFirstAvenueMember
     
Accumulated depreciation 12/31/2012 9,106us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineEightFirstAvenueMember
     
225 Cross Farm Lane [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) York, PA      
Encumbrances 17,214us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredAndTwentyFiveCrossFarmLaneMember
     
Initial Cost of Land 4,718us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredAndTwentyFiveCrossFarmLaneMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 23,163us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredAndTwentyFiveCrossFarmLaneMember
     
Land 4,715us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredAndTwentyFiveCrossFarmLaneMember
     
Building and improvements 23,166us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredAndTwentyFiveCrossFarmLaneMember
     
Total 27,881us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredAndTwentyFiveCrossFarmLaneMember
     
Accumulated depreciation 12/31/2012 4,204us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredAndTwentyFiveCrossFarmLaneMember
     
105 Steamboat Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Manchester, PA      
Initial Cost of Land 4,085us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredAndFiveSteamboatBlvdMember
     
Building and Improvements 14,464us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredAndFiveSteamboatBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredAndFiveSteamboatBlvdMember
     
Land 4,070us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredAndFiveSteamboatBlvdMember
     
Building and improvements 14,480us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredAndFiveSteamboatBlvdMember
     
Total 18,550us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredAndFiveSteamboatBlvdMember
     
Accumulated depreciation 12/31/2012 1,700us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredAndFiveSteamboatBlvdMember
     
20 Leo Lane [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) York County, PA      
Initial Cost of Land 6,884us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyLeoLaneMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 26,451us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyLeoLaneMember
     
Land 6,889us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyLeoLaneMember
     
Building and improvements 26,446us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyLeoLaneMember
     
Total 33,335us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyLeoLaneMember
     
Accumulated depreciation 12/31/2012 717us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwentyLeoLaneMember
     
720-730 Landwehr Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Northbrook, IL      
Initial Cost of Land 521us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyAndSevenHundredThirtyLandwehrRoadMember
     
Building and Improvements 2,982us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyAndSevenHundredThirtyLandwehrRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 783us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyAndSevenHundredThirtyLandwehrRoadMember
     
Land 521us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyAndSevenHundredThirtyLandwehrRoadMember
     
Building and improvements 3,765us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyAndSevenHundredThirtyLandwehrRoadMember
     
Total 4,286us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyAndSevenHundredThirtyLandwehrRoadMember
     
Accumulated depreciation 12/31/2012 1,723us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyAndSevenHundredThirtyLandwehrRoadMember
     
1385 101st Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lemont, IL      
Encumbrances 4,244us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
Initial Cost of Land 967us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
Building and Improvements 5,554us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,727us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
Land 968us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
Building and improvements 7,280us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
Total 8,248us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
Accumulated depreciation 12/31/2012 3,386us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenEightyFiveAndOneHundredOneStStreetMember
     
6750 South Sayre Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Bedford Park, IL      
Initial Cost of Land 224us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandSevenHundredFiftySouthSayreAvenueMember
     
Building and Improvements 1,309us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandSevenHundredFiftySouthSayreAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 470us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandSevenHundredFiftySouthSayreAvenueMember
     
Land 224us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandSevenHundredFiftySouthSayreAvenueMember
     
Building and improvements 1,779us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandSevenHundredFiftySouthSayreAvenueMember
     
Total 2,003us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandSevenHundredFiftySouthSayreAvenueMember
     
Accumulated depreciation 12/31/2012 826us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThousandSevenHundredFiftySouthSayreAvenueMember
     
585 Slawin Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Mount Prospect, IL      
Initial Cost of Land 611us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightyFiveSlawinCourtMember
     
Building and Improvements 3,505us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightyFiveSlawinCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 596us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightyFiveSlawinCourtMember
     
Land 525us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightyFiveSlawinCourtMember
     
Building and improvements 4,187us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightyFiveSlawinCourtMember
     
Total 4,712us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightyFiveSlawinCourtMember
     
Accumulated depreciation 12/31/2012 2,376us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightyFiveSlawinCourtMember
     
2300 Windsor Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Addison, IL      
Encumbrances 3,470us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
Initial Cost of Land 688us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
Building and Improvements 3,943us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 989us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
Land 696us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
Building and improvements 4,924us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
Total 5,620us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
Accumulated depreciation 12/31/2012 2,493us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandThreeHundredWindsorCourtMember
     
305-311 Era Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Northbrook, IL      
Initial Cost of Land 200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredFiveAndThreeHundredElevenEraDriveMember
     
Building and Improvements 1,154us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredFiveAndThreeHundredElevenEraDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,150us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredFiveAndThreeHundredElevenEraDriveMember
     
Land 205us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredFiveAndThreeHundredElevenEraDriveMember
     
Building and improvements 2,299us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredFiveAndThreeHundredElevenEraDriveMember
     
Total 2,504us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredFiveAndThreeHundredElevenEraDriveMember
     
Accumulated depreciation 12/31/2012 832us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredFiveAndThreeHundredElevenEraDriveMember
     
365 North Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carol Stream, IL      
Encumbrances 5,882us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
Initial Cost of Land 1,042us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
Building and Improvements 6,882us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,719us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
Land 1,073us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
Building and improvements 9,570us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
Total 10,643us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
Accumulated depreciation 12/31/2012 5,181us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSixtyFiveNorthAvenueMember
     
11241 Melrose Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Franklin Park, IL      
Initial Cost of Land 332us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFortyOneMelroseStreetMember
     
Building and Improvements 1,931us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFortyOneMelroseStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 78us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFortyOneMelroseStreetMember
     
Land 208us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFortyOneMelroseStreetMember
     
Building and improvements 2,133us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFortyOneMelroseStreetMember
     
Total 2,341us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFortyOneMelroseStreetMember
     
Accumulated depreciation 12/31/2012 1,291us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandTwoHundredFortyOneMelroseStreetMember
     
11939 South Central Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Alsip, IL      
Initial Cost of Land 1,208us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandNineHundredThirtyNineSCentralAvenueMember
     
Building and Improvements 6,843us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandNineHundredThirtyNineSCentralAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,657us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandNineHundredThirtyNineSCentralAvenueMember
     
Land 1,305us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandNineHundredThirtyNineSCentralAvenueMember
     
Building and improvements 9,403us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandNineHundredThirtyNineSCentralAvenueMember
     
Total 10,708us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandNineHundredThirtyNineSCentralAvenueMember
     
Accumulated depreciation 12/31/2012 3,942us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ElevenThousandNineHundredThirtyNineSCentralAvenueMember
     
1010-50 Sesame Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Bensenville, IL      
Initial Cost of Land 979us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTenAndFiftySesameStreetMember
     
Building and Improvements 5,546us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTenAndFiftySesameStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,720us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTenAndFiftySesameStreetMember
     
Land 1,048us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTenAndFiftySesameStreetMember
     
Building and improvements 9,197us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTenAndFiftySesameStreetMember
     
Total 10,245us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTenAndFiftySesameStreetMember
     
Accumulated depreciation 12/31/2012 3,223us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTenAndFiftySesameStreetMember
     
800 Business Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Mount Prospect, IL      
Initial Cost of Land 631us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredBusinessCenterDriveMember
     
Building and Improvements 3,493us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredBusinessCenterDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 328us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredBusinessCenterDriveMember
     
Land 666us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredBusinessCenterDriveMember
     
Building and improvements 3,786us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredBusinessCenterDriveMember
     
Total 4,452us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredBusinessCenterDriveMember
     
Accumulated depreciation 12/31/2012 1,328us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredBusinessCenterDriveMember
     
580 Slawin Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Mount Prospect, IL      
Encumbrances 781us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
Initial Cost of Land 233us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
Building and Improvements 1,292us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (37)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
Land 162us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
Building and improvements 1,326us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
Total 1,488us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
Accumulated depreciation 12/31/2012 551us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredEightySlawinCourtMember
     
1005 101st Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lemont, IL      
Encumbrances 6,131us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
Initial Cost of Land 1,200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
Building and Improvements 6,643us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,233us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
Land 1,220us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
Building and improvements 7,856us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
Total 9,076us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
Accumulated depreciation 12/31/2012 2,668us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenZeroFiveAndOneHundredOneStStreetMember
     
175 Wall Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Glendale Heights, IL      
Encumbrances 1,395us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
Initial Cost of Land 427us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
Building and Improvements 2,363us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 163us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
Land 433us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
Building and improvements 2,520us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
Total 2,953us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
Accumulated depreciation 12/31/2012 869us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneHundredSeventyFiveWallStreetMember
     
800-820 Thorndale Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Bensenville, IL      
Initial Cost of Land 751us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredAndEightHundredTwentyThorndaleAvenueMember
     
Building and Improvements 4,159us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredAndEightHundredTwentyThorndaleAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 812us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredAndEightHundredTwentyThorndaleAvenueMember
     
Land 761us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredAndEightHundredTwentyThorndaleAvenueMember
     
Building and improvements 4,961us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredAndEightHundredTwentyThorndaleAvenueMember
     
Total 5,722us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredAndEightHundredTwentyThorndaleAvenueMember
     
Accumulated depreciation 12/31/2012 1,476us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredAndEightHundredTwentyThorndaleAvenueMember
     
251 Airport Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) North Aurora, IL      
Encumbrances 4,998us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredFiftyOneAirportRoadMember
     
Initial Cost of Land 983us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredFiftyOneAirportRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 6,697us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredFiftyOneAirportRoadMember
     
Land 983us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredFiftyOneAirportRoadMember
     
Building and improvements 6,697us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredFiftyOneAirportRoadMember
     
Total 7,680us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredFiftyOneAirportRoadMember
     
Accumulated depreciation 12/31/2012 2,211us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoHundredFiftyOneAirportRoadMember
     
1661 Feehanville Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Mount Prospect, IL      
Initial Cost of Land 985us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredSixtyOneFeehanvilleDriveMember
     
Building and Improvements 5,455us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredSixtyOneFeehanvilleDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,252us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredSixtyOneFeehanvilleDriveMember
     
Land 1,044us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredSixtyOneFeehanvilleDriveMember
     
Building and improvements 8,648us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredSixtyOneFeehanvilleDriveMember
     
Total 9,692us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredSixtyOneFeehanvilleDriveMember
     
Accumulated depreciation 12/31/2012 2,968us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredSixtyOneFeehanvilleDriveMember
     
400 Crossroads Pkwy [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Bolingbrook, IL      
Encumbrances 5,429us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
Initial Cost of Land 1,178us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
Building and Improvements 9,453us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 808us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
Land 1,181us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
Building and improvements 10,258us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
Total 11,439us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
Accumulated depreciation 12/31/2012 3,105us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredCrossroadsPkwyMember
     
7609 W. Industrial Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Forest Park, IL      
Initial Cost of Land 1,207us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandSixHundredNineWIndustrialDriveMember
     
Building and Improvements 2,343us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandSixHundredNineWIndustrialDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 122us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandSixHundredNineWIndustrialDriveMember
     
Land 1,213us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandSixHundredNineWIndustrialDriveMember
     
Building and improvements 2,459us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandSixHundredNineWIndustrialDriveMember
     
Total 3,672us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandSixHundredNineWIndustrialDriveMember
     
Accumulated depreciation 12/31/2012 1,082us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandSixHundredNineWIndustrialDriveMember
     
7801 W. Industrial Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Forest Park, IL      
Initial Cost of Land 1,215us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandEightHundredOneWIndustrialDriveMember
     
Building and Improvements 3,020us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandEightHundredOneWIndustrialDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 476us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandEightHundredOneWIndustrialDriveMember
     
Land 1,220us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandEightHundredOneWIndustrialDriveMember
     
Building and improvements 3,491us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandEightHundredOneWIndustrialDriveMember
     
Total 4,711us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandEightHundredOneWIndustrialDriveMember
     
Accumulated depreciation 12/31/2012 1,656us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandEightHundredOneWIndustrialDriveMember
     
825 E. 26th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) LaGrange, IL      
Initial Cost of Land 1,547us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredTwentyFiveETwentySixThStreetMember
     
Building and Improvements 2,078us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredTwentyFiveETwentySixThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,474us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredTwentyFiveETwentySixThStreetMember
     
Land 1,617us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredTwentyFiveETwentySixThStreetMember
     
Building and improvements 4,482us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredTwentyFiveETwentySixThStreetMember
     
Total 6,099us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredTwentyFiveETwentySixThStreetMember
     
Accumulated depreciation 12/31/2012 2,185us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightHundredTwentyFiveETwentySixThStreetMember
     
725 Kimberly Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carol Stream, IL      
Initial Cost of Land 793us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyFiveKimberlyDriveMember
     
Building and Improvements 1,395us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyFiveKimberlyDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 223us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyFiveKimberlyDriveMember
     
Land 801us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyFiveKimberlyDriveMember
     
Building and improvements 1,610us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyFiveKimberlyDriveMember
     
Total 2,411us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyFiveKimberlyDriveMember
     
Accumulated depreciation 12/31/2012 580us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenHundredTwentyFiveKimberlyDriveMember
     
17001 S. Vincennes [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thornton, IL      
Initial Cost of Land 497us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneSVincennesMember
     
Building and Improvements 504us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneSVincennesMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 37us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneSVincennesMember
     
Land 513us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneSVincennesMember
     
Building and improvements 525us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneSVincennesMember
     
Total 1,038us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneSVincennesMember
     
Accumulated depreciation 12/31/2012 373us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneSVincennesMember
     
1111 Davis Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Elgin, IL      
Encumbrances 2,387us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
Initial Cost of Land 998us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
Building and Improvements 1,859us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 601us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
Land 1,046us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
Building and improvements 2,412us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
Total 3,458us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
Accumulated depreciation 12/31/2012 1,481us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredElevenDavisRoadMember
     
2900 W. 166th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Markham, IL      
Initial Cost of Land 1,132us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandNineHundredWOneHundredSixtySixThStreetMember
     
Building and Improvements 4,293us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandNineHundredWOneHundredSixtySixThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (881)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandNineHundredWOneHundredSixtySixThStreetMember
     
Land 1,134us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandNineHundredWOneHundredSixtySixThStreetMember
     
Building and improvements 3,410us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandNineHundredWOneHundredSixtySixThStreetMember
     
Total 4,544us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandNineHundredWOneHundredSixtySixThStreetMember
     
Accumulated depreciation 12/31/2012 806us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThousandNineHundredWOneHundredSixtySixThStreetMember
     
4100 Rock Creek Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Joliet, IL      
Initial Cost of Land 4,476us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneHundredRockCreekBlvdMember
     
Building and Improvements 16,061us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneHundredRockCreekBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 479us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneHundredRockCreekBlvdMember
     
Land 4,476us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneHundredRockCreekBlvdMember
     
Building and improvements 16,540us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneHundredRockCreekBlvdMember
     
Total 21,016us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneHundredRockCreekBlvdMember
     
Accumulated depreciation 12/31/2012 1,043us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneHundredRockCreekBlvdMember
     
555 W. Algonquin Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Arlington Heights, IL      
Encumbrances 2,021us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
Initial Cost of Land 574us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
Building and Improvements 741us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,936us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
Land 579us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
Building and improvements 2,672us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
Total 3,251us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
Accumulated depreciation 12/31/2012 703us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredFiftyFiveWAlgonquinRdMember
     
10100 58th Place [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Kenosha, WI      
Initial Cost of Land 4,201us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandOneHundredFiftyEightThPlaceMember
     
Building and Improvements 17,604us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandOneHundredFiftyEightThPlaceMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,443us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandOneHundredFiftyEightThPlaceMember
     
Land 4,201us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandOneHundredFiftyEightThPlaceMember
     
Building and improvements 19,047us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandOneHundredFiftyEightThPlaceMember
     
Total 23,248us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandOneHundredFiftyEightThPlaceMember
     
Accumulated depreciation 12/31/2012 1,417us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TenThousandOneHundredFiftyEightThPlaceMember
     
401 Airport Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) North Aurora, IL      
Initial Cost of Land 534us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneAirportRoadMember
     
Building and Improvements 1,957us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneAirportRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 0us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneAirportRoadMember
     
Land 534us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneAirportRoadMember
     
Building and improvements 1,957us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneAirportRoadMember
     
Total 2,491us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneAirportRoadMember
     
Accumulated depreciation 12/31/2012 54us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredOneAirportRoadMember
     
7000 W. 60th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Chicago, IL      
Initial Cost of Land 609us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandWSixtyThStreetMember
     
Building and Improvements 932us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandWSixtyThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 100us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandWSixtyThStreetMember
     
Land 667us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandWSixtyThStreetMember
     
Building and improvements 974us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandWSixtyThStreetMember
     
Total 1,641us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandWSixtyThStreetMember
     
Accumulated depreciation 12/31/2012 603us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandWSixtyThStreetMember
     
1501 Oakton Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Elk Grove Village, IL      
Encumbrances 7,391us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
Initial Cost of Land 3,369us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
Building and Improvements 6,121us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 434us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
Land 3,482us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
Building and improvements 6,442us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
Total 9,924us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
Accumulated depreciation 12/31/2012 1,535us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFiveHundredOneOaktonStreetMember
     
16500 W. 103rd Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Woodridge, IL      
Encumbrances 2,431us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
Initial Cost of Land 744us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
Building and Improvements 2,458us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 366us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
Land 762us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
Building and improvements 2,806us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
Total 3,568us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
Accumulated depreciation 12/31/2012 878us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandFiveHundredWOneHundredThreeRdStreetMember
     
8505 50th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Kenosha, WI      
Initial Cost of Land 3,212us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveFiftyThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 32,953us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveFiftyThStreetMember
     
Land 3,212us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveFiftyThStreetMember
     
Building and improvements 32,953us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveFiftyThStreetMember
     
Total 36,165us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveFiftyThStreetMember
     
Accumulated depreciation 12/31/2012 4,850us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveFiftyThStreetMember
     
9900-9970 Princeton [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Cincinnati, OH      
Encumbrances 3,643us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
Initial Cost of Land 545us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
Building and Improvements 3,088us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,759us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
Land 566us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
Building and improvements 4,826us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
Total 5,392us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
Accumulated depreciation 12/31/2012 2,083us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandNineHundredAndNineThousandNineHundredSeventyPrincetonMember
     
4700-4750 Creek Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Blue Ash, OH      
Initial Cost of Land 1,080us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredAndFourThousandSevenHundredFiftyCreekRoadMember
     
Building and Improvements 6,118us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredAndFourThousandSevenHundredFiftyCreekRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,346us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredAndFourThousandSevenHundredFiftyCreekRoadMember
     
Land 1,109us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredAndFourThousandSevenHundredFiftyCreekRoadMember
     
Building and improvements 7,435us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredAndFourThousandSevenHundredFiftyCreekRoadMember
     
Total 8,544us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredAndFourThousandSevenHundredFiftyCreekRoadMember
     
Accumulated depreciation 12/31/2012 3,273us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredAndFourThousandSevenHundredFiftyCreekRoadMember
     
4436 Mulhauser Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hamilton, OH      
Encumbrances 3,707us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtySixMulhauserRoadMember
     
Initial Cost of Land 630us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtySixMulhauserRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 5,375us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtySixMulhauserRoadMember
     
Land 630us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtySixMulhauserRoadMember
     
Building and improvements 5,375us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtySixMulhauserRoadMember
     
Total 6,005us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtySixMulhauserRoadMember
     
Accumulated depreciation 12/31/2012 1,657us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtySixMulhauserRoadMember
     
4438 Mulhauser Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hamilton, OH      
Encumbrances 4,581us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtyEightMulhauserRoadMember
     
Initial Cost of Land 779us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtyEightMulhauserRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 6,579us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtyEightMulhauserRoadMember
     
Land 779us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtyEightMulhauserRoadMember
     
Building and improvements 6,579us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtyEightMulhauserRoadMember
     
Total 7,358us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtyEightMulhauserRoadMember
     
Accumulated depreciation 12/31/2012 2,116us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandFourHundredThirtyEightMulhauserRoadMember
     
420 Wards Corner Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Loveland, OH      
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyWardsCornerRoadMember
     
Building and Improvements 1,083us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyWardsCornerRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 757us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyWardsCornerRoadMember
     
Land 606us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyWardsCornerRoadMember
     
Building and improvements 1,834us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyWardsCornerRoadMember
     
Total 2,440us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyWardsCornerRoadMember
     
Accumulated depreciation 12/31/2012 586us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyWardsCornerRoadMember
     
422 Wards Corner Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Loveland, OH      
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyTwoWardsCornerRoadMember
     
Building and Improvements 1,811us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyTwoWardsCornerRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 35us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyTwoWardsCornerRoadMember
     
Land 592us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyTwoWardsCornerRoadMember
     
Building and improvements 1,854us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyTwoWardsCornerRoadMember
     
Total 2,446us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyTwoWardsCornerRoadMember
     
Accumulated depreciation 12/31/2012 586us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredTwentyTwoWardsCornerRoadMember
     
4663 Dues Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Initial Cost of Land 858us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredSixtyThreeDuesDriveMember
     
Building and Improvements 2,273us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredSixtyThreeDuesDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 620us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredSixtyThreeDuesDriveMember
     
Land 875us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredSixtyThreeDuesDriveMember
     
Building and improvements 2,876us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredSixtyThreeDuesDriveMember
     
Total 3,751us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredSixtyThreeDuesDriveMember
     
Accumulated depreciation 12/31/2012 2,393us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSixHundredSixtyThreeDuesDriveMember
     
9345 Princeton-Glendale [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Encumbrances 1,530us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
Initial Cost of Land 818us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
Building and Improvements 1,648us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 380us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
Land 840us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
Building and improvements 2,006us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
Total 2,846us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
Accumulated depreciation 12/31/2012 1,098us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandThreeHundredFortyFivePrincetonGlendaleMember
     
9525 Glades Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Initial Cost of Land 347us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandFiveHundredTwentyFiveGladesDriveMember
     
Building and Improvements 1,323us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandFiveHundredTwentyFiveGladesDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 115us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandFiveHundredTwentyFiveGladesDriveMember
     
Land 355us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandFiveHundredTwentyFiveGladesDriveMember
     
Building and improvements 1,430us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandFiveHundredTwentyFiveGladesDriveMember
     
Total 1,785us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandFiveHundredTwentyFiveGladesDriveMember
     
Accumulated depreciation 12/31/2012 585us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandFiveHundredTwentyFiveGladesDriveMember
     
9776-9876 Windisch Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Initial Cost of Land 392us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredSeventyFourAndNineThousandSevenHundredNinetyTwoWindischRoadMember
     
Building and Improvements 1,744us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredSeventyFourAndNineThousandSevenHundredNinetyTwoWindischRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 78us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredSeventyFourAndNineThousandSevenHundredNinetyTwoWindischRoadMember
     
Land 394us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredSeventyFourAndNineThousandSevenHundredNinetyTwoWindischRoadMember
     
Building and improvements 1,820us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredSeventyFourAndNineThousandSevenHundredNinetyTwoWindischRoadMember
     
Total 2,214us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredSeventyFourAndNineThousandSevenHundredNinetyTwoWindischRoadMember
     
Accumulated depreciation 12/31/2012 566us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandSevenHundredSeventyFourAndNineThousandSevenHundredNinetyTwoWindischRoadMember
     
9808-9830 Windisch Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Initial Cost of Land 395us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredEightAndNineThousandEightHundredThirtyWindischRoadMember
     
Building and Improvements 2,541us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredEightAndNineThousandEightHundredThirtyWindischRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 85us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredEightAndNineThousandEightHundredThirtyWindischRoadMember
     
Land 397us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredEightAndNineThousandEightHundredThirtyWindischRoadMember
     
Building and improvements 2,624us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredEightAndNineThousandEightHundredThirtyWindischRoadMember
     
Total 3,021us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredEightAndNineThousandEightHundredThirtyWindischRoadMember
     
Accumulated depreciation 12/31/2012 617us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredEightAndNineThousandEightHundredThirtyWindischRoadMember
     
9842-9862 Windisch Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Initial Cost of Land 506us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredFortyTwoAndNineThousandEightHundredSixtyTwoWindischRoadMember
     
Building and Improvements 3,148us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredFortyTwoAndNineThousandEightHundredSixtyTwoWindischRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 102us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredFortyTwoAndNineThousandEightHundredSixtyTwoWindischRoadMember
     
Land 508us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredFortyTwoAndNineThousandEightHundredSixtyTwoWindischRoadMember
     
Building and improvements 3,248us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredFortyTwoAndNineThousandEightHundredSixtyTwoWindischRoadMember
     
Total 3,756us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredFortyTwoAndNineThousandEightHundredSixtyTwoWindischRoadMember
     
Accumulated depreciation 12/31/2012 796us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThousandEightHundredFortyTwoAndNineThousandEightHundredSixtyTwoWindischRoadMember
     
9872-9898 Windisch Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Initial Cost of Land 546us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightSevenTwoToNineEightNineEightWindischRoadMember
     
Building and Improvements 3,039us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightSevenTwoToNineEightNineEightWindischRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 159us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightSevenTwoToNineEightNineEightWindischRoadMember
     
Land 548us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightSevenTwoToNineEightNineEightWindischRoadMember
     
Building and improvements 3,196us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightSevenTwoToNineEightNineEightWindischRoadMember
     
Total 3,744us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightSevenTwoToNineEightNineEightWindischRoadMember
     
Accumulated depreciation 12/31/2012 812us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightSevenTwoToNineEightNineEightWindischRoadMember
     
9902-9922 Windisch Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westchester, OH      
Initial Cost of Land 623us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroTwoToNineNineTwoTwoWindischRoadMember
     
Building and Improvements 4,003us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroTwoToNineNineTwoTwoWindischRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 729us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroTwoToNineNineTwoTwoWindischRoadMember
     
Land 627us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroTwoToNineNineTwoTwoWindischRoadMember
     
Building and improvements 4,728us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroTwoToNineNineTwoTwoWindischRoadMember
     
Total 5,355us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroTwoToNineNineTwoTwoWindischRoadMember
     
Accumulated depreciation 12/31/2012 1,503us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroTwoToNineNineTwoTwoWindischRoadMember
     
30311 Emerald Valley Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Glenwillow, OH      
Encumbrances 8,914us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
Initial Cost of Land 681us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
Building and Improvements 11,838us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 845us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
Land 691us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
Building and improvements 12,673us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
Total 13,364us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
Accumulated depreciation 12/31/2012 3,862us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeOneOneEmeraldValleyParkwayMember
     
30333 Emerald Valley Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Glenwillow, OH      
Encumbrances 3,896us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
Initial Cost of Land 466us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
Building and Improvements 5,447us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 54us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
Land 475us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
Building and improvements 5,492us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
Total 5,967us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
Accumulated depreciation 12/31/2012 1,876us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeThreeThreeEmeraldValleyPkwyMember
     
7800 Cochran Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Glenwillow, OH      
Encumbrances 3,897us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
Initial Cost of Land 972us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
Building and Improvements 7,033us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 243us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
Land 991us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
Building and improvements 7,257us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
Total 8,248us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
Accumulated depreciation 12/31/2012 2,123us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightZeroZeroCochranRoadMember
     
7900 Cochran Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Glenwillow, OH      
Encumbrances 4,794us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
Initial Cost of Land 775us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
Building and Improvements 6,244us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 237us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
Land 792us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
Building and improvements 6,464us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
Total 7,256us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
Accumulated depreciation 12/31/2012 1,900us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroZeroCochranRoadMember
     
7905 Cochran Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Glenwillow, OH      
Initial Cost of Land 920us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroFiveCochranRoadMember
     
Building and Improvements 6,174us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroFiveCochranRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 691us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroFiveCochranRoadMember
     
Land 921us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroFiveCochranRoadMember
     
Building and improvements 6,864us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroFiveCochranRoadMember
     
Total 7,785us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroFiveCochranRoadMember
     
Accumulated depreciation 12/31/2012 2,210us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroFiveCochranRoadMember
     
30600 Carter Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Solon, OH      
Initial Cost of Land 989us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroZeroCarterStreetMember
     
Building and Improvements 3,042us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroZeroCarterStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 881us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroZeroCarterStreetMember
     
Land 1,022us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroZeroCarterStreetMember
     
Building and improvements 3,890us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroZeroCarterStreetMember
     
Total 4,912us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroZeroCarterStreetMember
     
Accumulated depreciation 12/31/2012 2,487us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroSixZeroZeroCarterStreetMember
     
8181 Darrow Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Twinsburg, OH      
Encumbrances 6,983us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
Initial Cost of Land 2,478us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
Building and Improvements 6,791us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,040us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
Land 2,496us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
Building and improvements 8,813us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
Total 11,309us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
Accumulated depreciation 12/31/2012 3,351us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneEightOneDarrowRoadMember
     
4785 Elati [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 173us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenEightFiveElatiMember
     
Building and Improvements 981us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenEightFiveElatiMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 205us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenEightFiveElatiMember
     
Land 175us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenEightFiveElatiMember
     
Building and improvements 1,184us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenEightFiveElatiMember
     
Total 1,359us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenEightFiveElatiMember
     
Accumulated depreciation 12/31/2012 481us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenEightFiveElatiMember
     
4770 Fox Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 132us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenZeroFoxStreetMember
     
Building and Improvements 750us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenZeroFoxStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 332us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenZeroFoxStreetMember
     
Land 134us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenZeroFoxStreetMember
     
Building and improvements 1,080us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenZeroFoxStreetMember
     
Total 1,214us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenZeroFoxStreetMember
     
Accumulated depreciation 12/31/2012 423us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenZeroFoxStreetMember
     
3851-3871 Revere [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Encumbrances   1,271us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
   
Initial Cost of Land 361us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
     
Building and Improvements 2,047us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 363us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
     
Land 368us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
     
Building and improvements 2,403us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
     
Total 2,771us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
     
Accumulated depreciation 12/31/2012 983us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightFiveOneThreeEightSevenOneRevereMember
     
4570 Ivy Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 219us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveSevenZeroIvyStreetMember
     
Building and Improvements 1,239us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveSevenZeroIvyStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 279us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveSevenZeroIvyStreetMember
     
Land 220us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveSevenZeroIvyStreetMember
     
Building and improvements 1,517us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveSevenZeroIvyStreetMember
     
Total 1,737us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveSevenZeroIvyStreetMember
     
Accumulated depreciation 12/31/2012 649us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveSevenZeroIvyStreetMember
     
5855 Stapleton Drive North [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 288us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightFiveFiveStapletonDriveNorthMember
     
Building and Improvements 1,630us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightFiveFiveStapletonDriveNorthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 249us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightFiveFiveStapletonDriveNorthMember
     
Land 290us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightFiveFiveStapletonDriveNorthMember
     
Building and improvements 1,877us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightFiveFiveStapletonDriveNorthMember
     
Total 2,167us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightFiveFiveStapletonDriveNorthMember
     
Accumulated depreciation 12/31/2012 780us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightFiveFiveStapletonDriveNorthMember
     
5885 Stapleton Drive North [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 376us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightEightFiveStapletonDriveNorthMember
     
Building and Improvements 2,129us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightEightFiveStapletonDriveNorthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 316us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightEightFiveStapletonDriveNorthMember
     
Land 380us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightEightFiveStapletonDriveNorthMember
     
Building and improvements 2,441us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightEightFiveStapletonDriveNorthMember
     
Total 2,821us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightEightFiveStapletonDriveNorthMember
     
Accumulated depreciation 12/31/2012 987us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightEightFiveStapletonDriveNorthMember
     
5977 North Broadway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Encumbrances   1,415us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
   
Initial Cost of Land 268us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
     
Building and Improvements 1,518us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 506us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
     
Land 271us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
     
Building and improvements 2,021us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
     
Total 2,292us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
     
Accumulated depreciation 12/31/2012 794us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineSevenSevenNorthBroadwayMember
     
5952-5978 North Broadway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Encumbrances   2,262us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
   
Initial Cost of Land 414us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
     
Building and Improvements 2,346us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 904us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
     
Land 422us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
     
Building and improvements 3,242us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
     
Total 3,664us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
     
Accumulated depreciation 12/31/2012 1,439us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveNineFiveTwoFiveNineSevenEightNorthBroadwayMember
     
4721 Ironton Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 232us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoOneIrontonStreetMember
     
Building and Improvements 1,313us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoOneIrontonStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 319us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoOneIrontonStreetMember
     
Land 236us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoOneIrontonStreetMember
     
Building and improvements 1,628us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoOneIrontonStreetMember
     
Total 1,864us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoOneIrontonStreetMember
     
Accumulated depreciation 12/31/2012 665us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoOneIrontonStreetMember
     
7003 E 47th Ave Drive [Member ]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 441us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroZeroThreeFourSeventhAveDriveMember
     
Building and Improvements 2,689us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroZeroThreeFourSeventhAveDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 58us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroZeroThreeFourSeventhAveDriveMember
     
Land 441us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroZeroThreeFourSeventhAveDriveMember
     
Building and improvements 2,747us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroZeroThreeFourSeventhAveDriveMember
     
Total 3,188us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroZeroThreeFourSeventhAveDriveMember
     
Accumulated depreciation 12/31/2012 1,189us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroZeroThreeFourSeventhAveDriveMember
     
9500 West 49th Street - A [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Wheatridge, CO      
Initial Cost of Land 283us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetMember
     
Building and Improvements 1,625us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 120us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetMember
     
Land 287us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetMember
     
Building and improvements 1,741us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetMember
     
Total 2,028us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetMember
     
Accumulated depreciation 12/31/2012 775us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetMember
     
9500 West 49th Street - B [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Wheatridge, CO      
Initial Cost of Land 225us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetBMember
     
Building and Improvements 1,272us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetBMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 200us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetBMember
     
Land 227us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetBMember
     
Building and improvements 1,470us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetBMember
     
Total 1,697us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetBMember
     
Accumulated depreciation 12/31/2012 603us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetBMember
     
9500 West 49th Street - C [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Wheatridge, CO      
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetCMember
     
Building and Improvements 3,409us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetCMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 163us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetCMember
     
Land 601us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetCMember
     
Building and improvements 3,571us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetCMember
     
Total 4,172us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetCMember
     
Accumulated depreciation 12/31/2012 1,567us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetCMember
     
9500 West 49th Street - D [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Wheatridge, CO      
Initial Cost of Land 246us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetDMember
     
Building and Improvements 1,537us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 487us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetDMember
     
Land 247us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetDMember
     
Building and improvements 2,023us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetDMember
     
Total 2,270us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetDMember
     
Accumulated depreciation 12/31/2012 927us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineFiveZeroZeroWestFourNinthStreetDMember
     
451-591 East 124th Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Littleton, CO      
Initial Cost of Land 383us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveNineOneEastOneTwoFourThAvenueMember
     
Building and Improvements 2,145us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveNineOneEastOneTwoFourThAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 481us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveNineOneEastOneTwoFourThAvenueMember
     
Land 383us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveNineOneEastOneTwoFourThAvenueMember
     
Building and improvements 2,626us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveNineOneEastOneTwoFourThAvenueMember
     
Total 3,009us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveNineOneEastOneTwoFourThAvenueMember
     
Accumulated depreciation 12/31/2012 1,096us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveNineOneEastOneTwoFourThAvenueMember
     
15000 West 6th Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Golden, CO      
Initial Cost of Land 913us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroZeroWestSixThAvenueMember
     
Building and Improvements 5,174us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroZeroWestSixThAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,147us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroZeroWestSixThAvenueMember
     
Land 918us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroZeroWestSixThAvenueMember
     
Building and improvements 6,316us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroZeroWestSixThAvenueMember
     
Total 7,234us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroZeroWestSixThAvenueMember
     
Accumulated depreciation 12/31/2012 2,824us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroZeroWestSixThAvenueMember
     
14998 West 6th Avenue Bldg E [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Golden, CO      
Initial Cost of Land 565us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgEMember
     
Building and Improvements 3,199us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgEMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 371us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgEMember
     
Land 570us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgEMember
     
Building and improvements 3,565us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgEMember
     
Total 4,135us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgEMember
     
Accumulated depreciation 12/31/2012 1,486us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgEMember
     
14998 West 6 th Avenue Bldg F [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Englewood, CO      
Initial Cost of Land 269us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgFMember
     
Building and Improvements 1,525us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgFMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 101us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgFMember
     
Land 273us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgFMember
     
Building and improvements 1,622us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgFMember
     
Total 1,895us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgFMember
     
Accumulated depreciation 12/31/2012 698us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourNineNineEightWestSixThAvenueBldgFMember
     
6547 South Racine Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Englewood, CO      
Encumbrances   2,703us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
   
Initial Cost of Land 739us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
     
Building and Improvements 4,241us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 170us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
     
Land 739us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
     
Building and improvements 4,411us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
     
Total 5,150us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
     
Accumulated depreciation 12/31/2012 1,868us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFourSevenSouthRacineCircleMember
     
11701 East 53rd Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 416us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenZeroOneEastFiveThreeRdAvenueMember
     
Building and Improvements 2,355us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenZeroOneEastFiveThreeRdAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 414us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenZeroOneEastFiveThreeRdAvenueMember
     
Land 422us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenZeroOneEastFiveThreeRdAvenueMember
     
Building and improvements 2,763us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenZeroOneEastFiveThreeRdAvenueMember
     
Total 3,185us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenZeroOneEastFiveThreeRdAvenueMember
     
Accumulated depreciation 12/31/2012 1,145us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenZeroOneEastFiveThreeRdAvenueMember
     
5401 Oswego [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 273us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourOneZeroOswegoStreetMember
     
Building and Improvements 1,547us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourOneZeroOswegoStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 313us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourOneZeroOswegoStreetMember
     
Land 278us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourOneZeroOswegoStreetMember
     
Building and improvements 1,855us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourOneZeroOswegoStreetMember
     
Total 2,133us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourOneZeroOswegoStreetMember
     
Accumulated depreciation 12/31/2012 798us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourOneZeroOswegoStreetMember
     
14818 West 6th Avenue Bldg A [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Golden, CO      
Initial Cost of Land 468us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightOneEightWestSixThAvenueBldgAMember
     
Building and Improvements 2,799us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightOneEightWestSixThAvenueBldgAMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 278us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightOneEightWestSixThAvenueBldgAMember
     
Land 468us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightOneEightWestSixThAvenueBldgAMember
     
Building and improvements 3,077us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightOneEightWestSixThAvenueBldgAMember
     
Total 3,545us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightOneEightWestSixThAvenueBldgAMember
     
Accumulated depreciation 12/31/2012 1,277us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightOneEightWestSixThAvenueBldgAMember
     
14828 West 6th Avenue Bldg B [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Golden, CO      
Initial Cost of Land 503us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightTwoEightWestSixthAvenueBldgMember
     
Building and Improvements 2,942us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightTwoEightWestSixthAvenueBldgMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 397us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightTwoEightWestSixthAvenueBldgMember
     
Land 503us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightTwoEightWestSixthAvenueBldgMember
     
Building and improvements 3,339us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightTwoEightWestSixthAvenueBldgMember
     
Total 3,842us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightTwoEightWestSixthAvenueBldgMember
     
Accumulated depreciation 12/31/2012 1,442us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourEightTwoEightWestSixthAvenueBldgMember
     
445 Bryant Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Encumbrances   6,747us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
   
Initial Cost of Land 1,829us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
     
Building and Improvements 10,219us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,664us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
     
Land 1,829us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
     
Building and improvements 12,883us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
     
Total 14,712us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
     
Accumulated depreciation 12/31/2012 5,429us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyFiveBryantStreetMember
     
3811 Joliet [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 735us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandEightHundredElevenJolietMember
     
Building and Improvements 4,166us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandEightHundredElevenJolietMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 543us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandEightHundredElevenJolietMember
     
Land 752us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandEightHundredElevenJolietMember
     
Building and improvements 4,692us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandEightHundredElevenJolietMember
     
Total 5,444us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandEightHundredElevenJolietMember
     
Accumulated depreciation 12/31/2012 1,926us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandEightHundredElevenJolietMember
     
12055 E 49th Ave/4955 Peoria [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 298us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwelveThousandFiftyFiveEFortyNineThAveByFourThousandNineHundredFiftyFivePeoriaMember
     
Building and Improvements 1,688us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwelveThousandFiftyFiveEFortyNineThAveByFourThousandNineHundredFiftyFivePeoriaMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 529us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwelveThousandFiftyFiveEFortyNineThAveByFourThousandNineHundredFiftyFivePeoriaMember
     
Land 305us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwelveThousandFiftyFiveEFortyNineThAveByFourThousandNineHundredFiftyFivePeoriaMember
     
Building and improvements 2,210us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwelveThousandFiftyFiveEFortyNineThAveByFourThousandNineHundredFiftyFivePeoriaMember
     
Total 2,515us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwelveThousandFiftyFiveEFortyNineThAveByFourThousandNineHundredFiftyFivePeoriaMember
     
Accumulated depreciation 12/31/2012 892us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwelveThousandFiftyFiveEFortyNineThAveByFourThousandNineHundredFiftyFivePeoriaMember
     
4940 - 4950 Paris [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 152us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredFortyAndFourThousandNineHundredFiftyParisMember
     
Building and Improvements 861us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredFortyAndFourThousandNineHundredFiftyParisMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 285us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredFortyAndFourThousandNineHundredFiftyParisMember
     
Land 156us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredFortyAndFourThousandNineHundredFiftyParisMember
     
Building and improvements 1,142us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredFortyAndFourThousandNineHundredFiftyParisMember
     
Total 1,298us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredFortyAndFourThousandNineHundredFiftyParisMember
     
Accumulated depreciation 12/31/2012 469us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredFortyAndFourThousandNineHundredFiftyParisMember
     
4970 Paris [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Initial Cost of Land 95us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredSeventyParisMember
     
Building and Improvements 537us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredSeventyParisMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 101us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredSeventyParisMember
     
Land 97us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredSeventyParisMember
     
Building and improvements 636us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredSeventyParisMember
     
Total 733us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredSeventyParisMember
     
Accumulated depreciation 12/31/2012 256us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandNineHundredSeventyParisMember
     
7367 South Revere Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Englewood, CO      
Encumbrances   3,151us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
   
Initial Cost of Land 926us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
     
Building and Improvements 5,124us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 820us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
     
Land 934us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
     
Building and improvements 5,936us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
     
Total 6,870us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
     
Accumulated depreciation 12/31/2012 2,420us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandThreeHundredSixtySevenSouthRevereParkwayMember
     
8200 East Park Meadows Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lone Tree, CO      
Initial Cost of Land 1,297us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandTwoHundredEastParkMeadowsDriveMember
     
Building and Improvements 7,348us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandTwoHundredEastParkMeadowsDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,265us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandTwoHundredEastParkMeadowsDriveMember
     
Land 1,304us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandTwoHundredEastParkMeadowsDriveMember
     
Building and improvements 8,606us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandTwoHundredEastParkMeadowsDriveMember
     
Total 9,910us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandTwoHundredEastParkMeadowsDriveMember
     
Accumulated depreciation 12/31/2012 3,098us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandTwoHundredEastParkMeadowsDriveMember
     
3250 Quentin Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Aurora, CO      
Initial Cost of Land 1,220us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredFiftyQuentinMember
     
Building and Improvements 6,911us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredFiftyQuentinMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 782us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredFiftyQuentinMember
     
Land 1,230us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredFiftyQuentinMember
     
Building and improvements 7,683us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredFiftyQuentinMember
     
Total 8,913us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredFiftyQuentinMember
     
Accumulated depreciation 12/31/2012 2,655us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredFiftyQuentinMember
     
Highpoint Bus Ctr B [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Littleton, CO      
Initial Cost of Land 739us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_HighpointBusCtrBMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,308us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_HighpointBusCtrBMember
     
Land 781us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_HighpointBusCtrBMember
     
Building and improvements 3,266us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_HighpointBusCtrBMember
     
Total 4,047us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_HighpointBusCtrBMember
     
Accumulated depreciation 12/31/2012 971us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_HighpointBusCtrBMember
     
1130 W. 124th Ave. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westminster, CO      
Initial Cost of Land 441us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredThirtyWOneHundredTwentyFourThAveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,289us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredThirtyWOneHundredTwentyFourThAveMember
     
Land 441us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredThirtyWOneHundredTwentyFourThAveMember
     
Building and improvements 3,289us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredThirtyWOneHundredTwentyFourThAveMember
     
Total 3,730us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredThirtyWOneHundredTwentyFourThAveMember
     
Accumulated depreciation 12/31/2012 1,241us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandOneHundredThirtyWOneHundredTwentyFourThAveMember
     
1070 W. 124th Ave. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westminster, CO      
Initial Cost of Land 374us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSeventyWOneHundredTwentyFourThAveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,836us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSeventyWOneHundredTwentyFourThAveMember
     
Land 374us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSeventyWOneHundredTwentyFourThAveMember
     
Building and improvements 2,836us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSeventyWOneHundredTwentyFourThAveMember
     
Total 3,210us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSeventyWOneHundredTwentyFourThAveMember
     
Accumulated depreciation 12/31/2012 1,002us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSeventyWOneHundredTwentyFourThAveMember
     
1020 W. 124th Ave. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westminster, CO      
Initial Cost of Land 374us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwentyWOneHundredTwentyFourThAveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,809us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwentyWOneHundredTwentyFourThAveMember
     
Land 374us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwentyWOneHundredTwentyFourThAveMember
     
Building and improvements 2,809us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwentyWOneHundredTwentyFourThAveMember
     
Total 3,183us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwentyWOneHundredTwentyFourThAveMember
     
Accumulated depreciation 12/31/2012 949us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandTwentyWOneHundredTwentyFourThAveMember
     
8810 W. 116th Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Broomfield, CO      
Initial Cost of Land 312us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTenWestOneHundredSixteenThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,514us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTenWestOneHundredSixteenThStreetMember
     
Land 370us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTenWestOneHundredSixteenThStreetMember
     
Building and improvements 1,456us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTenWestOneHundredSixteenThStreetMember
     
Total 1,826us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTenWestOneHundredSixteenThStreetMember
     
Accumulated depreciation 12/31/2012 422us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTenWestOneHundredSixteenThStreetMember
     
960 W. 124th Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Westminster, CO      
Initial Cost of Land 441us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredSixtyWOneHundredTwentyFourThAveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,507us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredSixtyWOneHundredTwentyFourThAveMember
     
Land 442us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredSixtyWOneHundredTwentyFourThAveMember
     
Building and improvements 3,506us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredSixtyWOneHundredTwentyFourThAveMember
     
Total 3,948us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredSixtyWOneHundredTwentyFourThAveMember
     
Accumulated depreciation 12/31/2012 1,187us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredSixtyWOneHundredTwentyFourThAveMember
     
8820 W. 116th Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Broomfield, CO      
Initial Cost of Land 338us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTwentyWOneHundredSixteenThStreetMember
     
Building and Improvements 1,918us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTwentyWOneHundredSixteenThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 321us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTwentyWOneHundredSixteenThStreetMember
     
Land 372us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTwentyWOneHundredSixteenThStreetMember
     
Building and improvements 2,205us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTwentyWOneHundredSixteenThStreetMember
     
Total 2,577us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTwentyWOneHundredSixteenThStreetMember
     
Accumulated depreciation 12/31/2012 658us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredTwentyWOneHundredSixteenThStreetMember
     
8835 W. 116th Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Broomfield, CO      
Initial Cost of Land 1,151us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredThirtyFiveWOneHundredSixteenThStreetMember
     
Building and Improvements 6,523us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredThirtyFiveWOneHundredSixteenThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,410us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredThirtyFiveWOneHundredSixteenThStreetMember
     
Land 1,304us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredThirtyFiveWOneHundredSixteenThStreetMember
     
Building and improvements 7,780us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredThirtyFiveWOneHundredSixteenThStreetMember
     
Total 9,084us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredThirtyFiveWOneHundredSixteenThStreetMember
     
Accumulated depreciation 12/31/2012 2,445us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandEightHundredThirtyFiveWOneHundredSixteenThStreetMember
     
18150 E. 32nd Place [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Aurora, CO      
Encumbrances   1,824us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
   
Initial Cost of Land 563us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
     
Building and Improvements 3,188us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 226us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
     
Land 572us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
     
Building and improvements 3,405us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
     
Total 3,977us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
     
Accumulated depreciation 12/31/2012 1,105us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EighteenThousandOneHundredFiftyEThirtyTwoNdStreetMember
     
3400 Fraser Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Aurora, CO      
Encumbrances   2,155us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
   
Initial Cost of Land 616us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
     
Building and Improvements 3,593us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (184)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
     
Land 620us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
     
Building and improvements 3,405us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
     
Total 4,025us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
     
Accumulated depreciation 12/31/2012 1,005us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandFourHundredFraserStreetMember
     
7005 E. 46th Avenue Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Encumbrances   1,348us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
   
Initial Cost of Land 512us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
     
Building and Improvements 2,025us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 32us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
     
Land 517us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
     
Building and improvements 2,052us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
     
Total 2,569us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
     
Accumulated depreciation 12/31/2012 682us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiveEFortySixThAvenueDriveMember
     
4001 Salazar Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Frederick, CO      
Initial Cost of Land 1,271us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneSalazarWayMember
     
Building and Improvements 6,508us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneSalazarWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (773)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneSalazarWayMember
     
Land 1,276us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneSalazarWayMember
     
Building and improvements 5,730us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneSalazarWayMember
     
Total 7,006us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneSalazarWayMember
     
Accumulated depreciation 12/31/2012 1,360us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandOneSalazarWayMember
     
5909-5915 N. Broadway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Denver, CO      
Encumbrances   898us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
   
Initial Cost of Land 495us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
     
Building and Improvements 1,268us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 107us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
     
Land 500us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
     
Building and improvements 1,370us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
     
Total 1,870us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
     
Accumulated depreciation 12/31/2012 566us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThousandNineHundredNineAndFiveThousandNineHundredFifteenBroadwayMember
     
2406-2416 Walnut Ridge [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dallas, TX      
Initial Cost of Land 178us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroSixToTwoFourOneSixWalnutRidgeMember
     
Building and Improvements 1,006us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroSixToTwoFourOneSixWalnutRidgeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 633us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroSixToTwoFourOneSixWalnutRidgeMember
     
Land 172us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroSixToTwoFourOneSixWalnutRidgeMember
     
Building and improvements 1,645us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroSixToTwoFourOneSixWalnutRidgeMember
     
Total 1,817us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroSixToTwoFourOneSixWalnutRidgeMember
     
Accumulated depreciation 12/31/2012 603us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroSixToTwoFourOneSixWalnutRidgeMember
     
2401-2419 Walnut Ridge [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dallas, TX      
Initial Cost of Land 148us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneToTwoFourOneNineWalnutRidgeMember
     
Building and Improvements 839us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneToTwoFourOneNineWalnutRidgeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 416us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneToTwoFourOneNineWalnutRidgeMember
     
Land 142us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneToTwoFourOneNineWalnutRidgeMember
     
Building and improvements 1,261us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneToTwoFourOneNineWalnutRidgeMember
     
Total 1,403us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneToTwoFourOneNineWalnutRidgeMember
     
Accumulated depreciation 12/31/2012 441us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneToTwoFourOneNineWalnutRidgeMember
     
900-906 Great Southwest Pkwy [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Arlington, TX      
Initial Cost of Land 237us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroToNineZeroSixGreatSouthwestPkwyMember
     
Building and Improvements 1,342us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroToNineZeroSixGreatSouthwestPkwyMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 638us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroToNineZeroSixGreatSouthwestPkwyMember
     
Land 270us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroToNineZeroSixGreatSouthwestPkwyMember
     
Building and improvements 1,947us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroToNineZeroSixGreatSouthwestPkwyMember
     
Total 2,217us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroToNineZeroSixGreatSouthwestPkwyMember
     
Accumulated depreciation 12/31/2012 837us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroToNineZeroSixGreatSouthwestPkwyMember
     
3000 West Commerce [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dallas, TX      
Initial Cost of Land 456us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWestCommerceMember
     
Building and Improvements 2,584us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWestCommerceMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,225us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWestCommerceMember
     
Land 469us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWestCommerceMember
     
Building and improvements 3,796us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWestCommerceMember
     
Total 4,265us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWestCommerceMember
     
Accumulated depreciation 12/31/2012 1,498us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWestCommerceMember
     
3030 Hansboro [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dallas, TX      
Initial Cost of Land 266us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeZeroHansboroMember
     
Building and Improvements 1,510us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeZeroHansboroMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (664)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeZeroHansboroMember
     
Land 87us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeZeroHansboroMember
     
Building and improvements 1,025us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeZeroHansboroMember
     
Total 1,112us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeZeroHansboroMember
     
Accumulated depreciation 12/31/2012 643us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroThreeZeroHansboroMember
     
405-407 113th [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Arlington, TX      
Initial Cost of Land 181us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveToFourZeroSevenOneOneThreeMember
     
Building and Improvements 1,026us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveToFourZeroSevenOneOneThreeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 511us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveToFourZeroSevenOneOneThreeMember
     
Land 185us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveToFourZeroSevenOneOneThreeMember
     
Building and improvements 1,533us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveToFourZeroSevenOneOneThreeMember
     
Total 1,718us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveToFourZeroSevenOneOneThreeMember
     
Accumulated depreciation 12/31/2012 618us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroFiveToFourZeroSevenOneOneThreeMember
     
816 111th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Arlington, TX      
Encumbrances 857us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
Initial Cost of Land 251us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
Building and Improvements 1,421us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 195us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
Land 258us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
Building and improvements 1,609us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
Total 1,867us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
Accumulated depreciation 12/31/2012 700us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightOneSixOneOneOneStreetMember
     
7427 Dogwood Park [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 96us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenDogwoodParkMember
     
Building and Improvements 532us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenDogwoodParkMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 302us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenDogwoodParkMember
     
Land 102us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenDogwoodParkMember
     
Building and improvements 828us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenDogwoodParkMember
     
Total 930us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenDogwoodParkMember
     
Accumulated depreciation 12/31/2012 298us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenDogwoodParkMember
     
7348-54 Tower Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 88us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeFourEightToFiveFourTowerStreetMember
     
Building and Improvements 489us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeFourEightToFiveFourTowerStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 213us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeFourEightToFiveFourTowerStreetMember
     
Land 94us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeFourEightToFiveFourTowerStreetMember
     
Building and improvements 696us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeFourEightToFiveFourTowerStreetMember
     
Total 790us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeFourEightToFiveFourTowerStreetMember
     
Accumulated depreciation 12/31/2012 268us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeFourEightToFiveFourTowerStreetMember
     
7339-41 Tower Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 98us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeNineToFourOneTowerStreetMember
     
Building and Improvements 541us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeNineToFourOneTowerStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 180us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeNineToFourOneTowerStreetMember
     
Land 104us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeNineToFourOneTowerStreetMember
     
Building and improvements 715us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeNineToFourOneTowerStreetMember
     
Total 819us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeNineToFourOneTowerStreetMember
     
Accumulated depreciation 12/31/2012 266us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeNineToFourOneTowerStreetMember
     
7437-45 Tower Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 102us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSevenToFourFiveTowerStreetMember
     
Building and Improvements 563us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSevenToFourFiveTowerStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 294us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSevenToFourFiveTowerStreetMember
     
Land 108us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSevenToFourFiveTowerStreetMember
     
Building and improvements 851us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSevenToFourFiveTowerStreetMember
     
Total 959us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSevenToFourFiveTowerStreetMember
     
Accumulated depreciation 12/31/2012 302us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSevenToFourFiveTowerStreetMember
     
7331-59 Airport Freeway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Encumbrances 1,655us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
Initial Cost of Land 354us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
Building and Improvements 1,958us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 368us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
Land 372us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
Building and improvements 2,308us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
Total 2,680us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
Accumulated depreciation 12/31/2012 904us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeOneToFiveNineAirportFreewayMember
     
7338-60 Dogwood Park [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 106us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeEightToSixZeroDogwoodParkMember
     
Building and Improvements 587us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeEightToSixZeroDogwoodParkMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 244us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeEightToSixZeroDogwoodParkMember
     
Land 112us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeEightToSixZeroDogwoodParkMember
     
Building and improvements 825us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeEightToSixZeroDogwoodParkMember
     
Total 937us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeEightToSixZeroDogwoodParkMember
     
Accumulated depreciation 12/31/2012 289us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeThreeEightToSixZeroDogwoodParkMember
     
7450-70 Dogwood Park [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 106us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroToSevenZeroDogwoodParkMember
     
Building and Improvements 584us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroToSevenZeroDogwoodParkMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 136us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroToSevenZeroDogwoodParkMember
     
Land 112us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroToSevenZeroDogwoodParkMember
     
Building and improvements 714us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroToSevenZeroDogwoodParkMember
     
Total 826us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroToSevenZeroDogwoodParkMember
     
Accumulated depreciation 12/31/2012 273us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroToSevenZeroDogwoodParkMember
     
7423-49 Airport Freeway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Encumbrances 1,450us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
Initial Cost of Land 293us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
Building and Improvements 1,621us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 434us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
Land 308us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
Building and improvements 2,040us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
Total 2,348us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
Accumulated depreciation 12/31/2012 755us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoThreeToFourNineAirportFreewayMember
     
7400 Whitehall Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 109us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourZeroZeroWhitehallStreetMember
     
Building and Improvements 603us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourZeroZeroWhitehallStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 95us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourZeroZeroWhitehallStreetMember
     
Land 115us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourZeroZeroWhitehallStreetMember
     
Building and improvements 692us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourZeroZeroWhitehallStreetMember
     
Total 807us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourZeroZeroWhitehallStreetMember
     
Accumulated depreciation 12/31/2012 266us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourZeroZeroWhitehallStreetMember
     
1602-1654 Terre Colony [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dallas, TX      
Encumbrances 1,788us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
Initial Cost of Land 458us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
Building and Improvements 2,596us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 845us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
Land 468us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
Building and improvements 3,431us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
Total 3,899us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
Accumulated depreciation 12/31/2012 1,148us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixZeroTwoToOneSixFiveFourTerreColonyMember
     
2351-2355 Merritt Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 101us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveOneToTwoThreeFiveFiveMerrittDriveMember
     
Building and Improvements 574us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveOneToTwoThreeFiveFiveMerrittDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 104us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveOneToTwoThreeFiveFiveMerrittDriveMember
     
Land 92us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveOneToTwoThreeFiveFiveMerrittDriveMember
     
Building and improvements 687us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveOneToTwoThreeFiveFiveMerrittDriveMember
     
Total 779us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveOneToTwoThreeFiveFiveMerrittDriveMember
     
Accumulated depreciation 12/31/2012 242us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveOneToTwoThreeFiveFiveMerrittDriveMember
     
2220 Merritt Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 352us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoTwoZeroMerrittDriveMember
     
Building and Improvements 1,993us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoTwoZeroMerrittDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 145us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoTwoZeroMerrittDriveMember
     
Land 316us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoTwoZeroMerrittDriveMember
     
Building and improvements 2,174us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoTwoZeroMerrittDriveMember
     
Total 2,490us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoTwoZeroMerrittDriveMember
     
Accumulated depreciation 12/31/2012 661us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoTwoZeroMerrittDriveMember
     
2010 Merritt Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 350us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneZeroMerrittDriveMember
     
Building and Improvements 1,981us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneZeroMerrittDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 55us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneZeroMerrittDriveMember
     
Land 318us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneZeroMerrittDriveMember
     
Building and improvements 2,068us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneZeroMerrittDriveMember
     
Total 2,386us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneZeroMerrittDriveMember
     
Accumulated depreciation 12/31/2012 668us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneZeroMerrittDriveMember
     
2363 Merritt Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 73us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixThreeMerrittDriveMember
     
Building and Improvements 412us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixThreeMerrittDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (8)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixThreeMerrittDriveMember
     
Land 47us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixThreeMerrittDriveMember
     
Building and improvements 430us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixThreeMerrittDriveMember
     
Total 477us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixThreeMerrittDriveMember
     
Accumulated depreciation 12/31/2012 159us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixThreeMerrittDriveMember
     
2447 Merritt Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 70us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFourSevenMerrittDriveMember
     
Building and Improvements 395us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFourSevenMerrittDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (166)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFourSevenMerrittDriveMember
     
Land 23us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFourSevenMerrittDriveMember
     
Building and improvements 276us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFourSevenMerrittDriveMember
     
Total 299us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFourSevenMerrittDriveMember
     
Accumulated depreciation 12/31/2012 156us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFourSevenMerrittDriveMember
     
2465-2475 Merritt Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 91us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourSixFiveToTwoFourSevenFiveMerrittDriveMember
     
Building and Improvements 514us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourSixFiveToTwoFourSevenFiveMerrittDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 39us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourSixFiveToTwoFourSevenFiveMerrittDriveMember
     
Land 71us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourSixFiveToTwoFourSevenFiveMerrittDriveMember
     
Building and improvements 573us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourSixFiveToTwoFourSevenFiveMerrittDriveMember
     
Total 644us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourSixFiveToTwoFourSevenFiveMerrittDriveMember
     
Accumulated depreciation 12/31/2012 227us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourSixFiveToTwoFourSevenFiveMerrittDriveMember
     
2485-2505 Merritt Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 431us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveToTwoFiveZeroFiveMerrittDriveMember
     
Building and Improvements 2,440us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveToTwoFiveZeroFiveMerrittDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 762us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveToTwoFiveZeroFiveMerrittDriveMember
     
Land 426us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveToTwoFiveZeroFiveMerrittDriveMember
     
Building and improvements 3,207us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveToTwoFiveZeroFiveMerrittDriveMember
     
Total 3,633us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveToTwoFiveZeroFiveMerrittDriveMember
     
Accumulated depreciation 12/31/2012 1,196us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveToTwoFiveZeroFiveMerrittDriveMember
     
2110 Hutton Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carrolton, TX      
Initial Cost of Land 374us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneZeroHuttonDriveMember
     
Building and Improvements 2,117us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneZeroHuttonDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 117us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneZeroHuttonDriveMember
     
Land 255us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneZeroHuttonDriveMember
     
Building and improvements 2,353us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneZeroHuttonDriveMember
     
Total 2,608us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneZeroHuttonDriveMember
     
Accumulated depreciation 12/31/2012 844us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneZeroHuttonDriveMember
     
2025 McKenzie Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carrolton, TX      
Encumbrances 1,398us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
Initial Cost of Land 437us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
Building and Improvements 2,478us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 133us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
Land 442us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
Building and improvements 2,606us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
Total 3,048us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
Accumulated depreciation 12/31/2012 896us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoFiveMckenzieDriveMember
     
2019 McKenzie Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carrolton, TX      
Encumbrances 1,706us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
Initial Cost of Land 502us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
Building and Improvements 2,843us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 374us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
Land 507us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
Building and improvements 3,212us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
Total 3,719us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
Accumulated depreciation 12/31/2012 1,122us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneNineMckenzieDriveMember
     
2029-2035 McKenzie Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carrolton, TX      
Encumbrances 1,502us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
Initial Cost of Land 306us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
Building and Improvements 1,870us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 236us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
Land 306us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
Building and improvements 2,106us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
Total 2,412us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
Accumulated depreciation 12/31/2012 741us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroTwoNineToTwoZeroThreeFiveMckenzieDriveMember
     
2015 McKenzie Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carrolton, TX      
Encumbrances 2,475us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
Initial Cost of Land 510us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
Building and Improvements 2,891us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 402us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
Land 516us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
Building and improvements 3,287us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
Total 3,803us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
Accumulated depreciation 12/31/2012 1,109us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroOneFiveMckenzieDriveMember
     
2009 McKenzie Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carrolton, TX      
Encumbrances 2,404us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
Initial Cost of Land 476us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
Building and Improvements 2,699us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 519us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
Land 481us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
Building and improvements 3,213us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
Total 3,694us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
Accumulated depreciation 12/31/2012 1,092us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNineMckenzieDriveMember
     
900-1100 Avenue S [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Prairie, TX      
Encumbrances 2,344us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Initial Cost of Land 623us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Building and Improvements 3,528us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 959us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Land 629us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Building and improvements 4,481us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Total 5,110us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Accumulated depreciation 12/31/2012 1,250us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroZeroOneOneZeroZeroAvenueSMember
     
Plano Crossing [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Plano, TX      
Encumbrances 9,157us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
Initial Cost of Land 1,961us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
Building and Improvements 11,112us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 997us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
Land 1,981us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
Building and improvements 12,089us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
Total 14,070us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
Accumulated depreciation 12/31/2012 3,660us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_PlanoCrossingFMember
     
7413A-C Dogwood Park [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 110us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourOneThreeCDogwoodParkMember
     
Building and Improvements 623us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourOneThreeCDogwoodParkMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 245us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourOneThreeCDogwoodParkMember
     
Land 111us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourOneThreeCDogwoodParkMember
     
Building and improvements 867us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourOneThreeCDogwoodParkMember
     
Total 978us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourOneThreeCDogwoodParkMember
     
Accumulated depreciation 12/31/2012 269us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourOneThreeCDogwoodParkMember
     
7450 Tower Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 36us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroTowerStreetMember
     
Building and Improvements 204us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroTowerStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 103us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroTowerStreetMember
     
Land 36us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroTowerStreetMember
     
Building and improvements 307us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroTowerStreetMember
     
Total 343us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroTowerStreetMember
     
Accumulated depreciation 12/31/2012 111us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroTowerStreetMember
     
7436 Tower Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 57us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSixTowerStreetMember
     
Building and Improvements 324us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSixTowerStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 196us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSixTowerStreetMember
     
Land 58us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSixTowerStreetMember
     
Building and improvements 519us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSixTowerStreetMember
     
Total 577us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSixTowerStreetMember
     
Accumulated depreciation 12/31/2012 177us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourThreeSixTowerStreetMember
     
7426 Tower Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 76us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSixTowerStreetMember
     
Building and Improvements 429us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSixTowerStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 186us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSixTowerStreetMember
     
Land 76us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSixTowerStreetMember
     
Building and improvements 615us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSixTowerStreetMember
     
Total 691us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSixTowerStreetMember
     
Accumulated depreciation 12/31/2012 160us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSixTowerStreetMember
     
7427-7429 Tower Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 75us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenSevenFourTwoNineTowerStreetMember
     
Building and Improvements 427us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenSevenFourTwoNineTowerStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 163us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenSevenFourTwoNineTowerStreetMember
     
Land 76us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenSevenFourTwoNineTowerStreetMember
     
Building and improvements 589us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenSevenFourTwoNineTowerStreetMember
     
Total 665us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenSevenFourTwoNineTowerStreetMember
     
Accumulated depreciation 12/31/2012 219us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourTwoSevenSevenFourTwoNineTowerStreetMember
     
2840-2842 Handley Ederville Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 112us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourZeroTwoEightFourTwoHandleyEdervilleRdMember
     
Building and Improvements 635us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourZeroTwoEightFourTwoHandleyEdervilleRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 52us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourZeroTwoEightFourTwoHandleyEdervilleRdMember
     
Land 113us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourZeroTwoEightFourTwoHandleyEdervilleRdMember
     
Building and improvements 686us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourZeroTwoEightFourTwoHandleyEdervilleRdMember
     
Total 799us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourZeroTwoEightFourTwoHandleyEdervilleRdMember
     
Accumulated depreciation 12/31/2012 208us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourZeroTwoEightFourTwoHandleyEdervilleRdMember
     
825-827 Avenue H D [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Arlington, TX      
Encumbrances 2,481us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
Building and Improvements 3,006us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 67us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
Land 604us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
Building and improvements 3,069us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
Total 3,673us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
Accumulated depreciation 12/31/2012 1,229us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightTwoFiveEightTwoSevenAvenueHDMember
     
1200-16 Avenue H D [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Arlington, TX      
Encumbrances 1,731us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
Building and Improvements 2,846us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 329us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
Land 604us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
Building and improvements 3,171us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
Total 3,775us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
Accumulated depreciation 12/31/2012 928us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoZeroZeroOneSixAvenueHDMember
     
1322-66 W. North Carrier Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Prairie, TX      
Encumbrances 4,739us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
Initial Cost of Land 1,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
Building and Improvements 5,012us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,003us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
Land 1,006us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
Building and improvements 6,009us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
Total 7,015us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
Accumulated depreciation 12/31/2012 1,796us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoSixSixNCarrierParkwayEMember
     
2401-2407 Centennial Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Arlington, TX      
Encumbrances   2,143us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
   
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
     
Building and Improvements 2,534us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (50)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
     
Land 604us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
     
Building and improvements 2,480us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
     
Total 3,084us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
     
Accumulated depreciation 12/31/2012 991us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroOneTwoFourZeroSevenCentennialMember
     
3111 West Commerce Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Dallas, TX      
Encumbrances   3,802us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
   
Initial Cost of Land 1,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
     
Building and Improvements 3,364us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,264us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
     
Land 1,011us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
     
Building and improvements 4,617us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
     
Total 5,628us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
     
Accumulated depreciation 12/31/2012 1,419us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeOneOneOneWestCommerceMember
     
13800 Senlac Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmers Ranch, TX      
Encumbrances   3,142us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
   
Initial Cost of Land 823us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
     
Building and Improvements 4,042us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (214)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
     
Land 825us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
     
Building and improvements 3,826us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
     
Total 4,651us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
     
Accumulated depreciation 12/31/2012 1,306us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeEightZeroZeroSenlacDriveMember
     
801-831 S Great Southwest Pkwy [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Prairie, TX      
Initial Cost of Land 2,581us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneEightThreeOneSGreatSouthwestGMember
     
Building and Improvements 16,556us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneEightThreeOneSGreatSouthwestGMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 53us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneEightThreeOneSGreatSouthwestGMember
     
Land 2,586us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneEightThreeOneSGreatSouthwestGMember
     
Building and improvements 16,604us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneEightThreeOneSGreatSouthwestGMember
     
Total 19,190us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneEightThreeOneSGreatSouthwestGMember
     
Accumulated depreciation 12/31/2012 7,867us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneEightThreeOneSGreatSouthwestGMember
     
801 Heinz Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Prairie, TX      
Encumbrances   2,618us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
   
Initial Cost of Land 599us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
     
Building and Improvements 3,327us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 315us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
     
Land 601us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
     
Building and improvements 3,640us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
     
Total 4,241us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
     
Accumulated depreciation 12/31/2012 1,338us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneHeinzWayMember
     
901-937 Heinz Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Prairie, TX      
Encumbrances   2,035us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
   
Initial Cost of Land 493us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
     
Building and Improvements 2,758us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 45us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
     
Land 481us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
     
Building and improvements 2,815us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
     
Total 3,296us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
     
Accumulated depreciation 12/31/2012 1,101us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroOneNineThreeSevenHeinzWayMember
     
3301 Century Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Irving, TX      
Encumbrances   2,110us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
   
Initial Cost of Land 760us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
     
Building and Improvements 3,856us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (16)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
     
Land 771us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
     
Building and improvements 3,829us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
     
Total 4,600us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
     
Accumulated depreciation 12/31/2012 867us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeZeroOneCenturyCircleMember
     
3901 W Miller Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Garland, TX      
Initial Cost of Land 1,912us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineZeroOneWestMillerRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 15,478us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineZeroOneWestMillerRoadMember
     
Land 1,947us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineZeroOneWestMillerRoadMember
     
Building and improvements 15,443us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineZeroOneWestMillerRoadMember
     
Total 17,390us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineZeroOneWestMillerRoadMember
     
Accumulated depreciation 12/31/2012 2,955us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineZeroOneWestMillerRoadMember
     
1731 Thorncroft [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 331us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredThirtyOneThorncroftMember
     
Building and Improvements 1,904us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredThirtyOneThorncroftMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 189us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredThirtyOneThorncroftMember
     
Land 331us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredThirtyOneThorncroftMember
     
Building and improvements 2,093us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredThirtyOneThorncroftMember
     
Total 2,424us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredThirtyOneThorncroftMember
     
Accumulated depreciation 12/31/2012 1,050us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredThirtyOneThorncroftMember
     
47461 Clipper [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Plymouth Township, MI      
Initial Cost of Land 122us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FortySevenThousandFourHundredSixtyOneClipperMember
     
Building and Improvements 723us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FortySevenThousandFourHundredSixtyOneClipperMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 54us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FortySevenThousandFourHundredSixtyOneClipperMember
     
Land 122us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FortySevenThousandFourHundredSixtyOneClipperMember
     
Building and improvements 777us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FortySevenThousandFourHundredSixtyOneClipperMember
     
Total 899us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FortySevenThousandFourHundredSixtyOneClipperMember
     
Accumulated depreciation 12/31/2012 409us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FortySevenThousandFourHundredSixtyOneClipperMember
     
449 Executive Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 125us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyNineExecutiveDriveMember
     
Building and Improvements 425us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyNineExecutiveDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,066us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyNineExecutiveDriveMember
     
Land 218us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyNineExecutiveDriveMember
     
Building and improvements 1,398us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyNineExecutiveDriveMember
     
Total 1,616us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyNineExecutiveDriveMember
     
Accumulated depreciation 12/31/2012 1,268us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFortyNineExecutiveDriveMember
     
501 Executive Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 71us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredOneExecutiveDriveMember
     
Building and Improvements 236us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredOneExecutiveDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 678us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredOneExecutiveDriveMember
     
Land 129us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredOneExecutiveDriveMember
     
Building and improvements 856us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredOneExecutiveDriveMember
     
Total 985us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredOneExecutiveDriveMember
     
Accumulated depreciation 12/31/2012 659us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveHundredOneExecutiveDriveMember
     
451 Robbins Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 96us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFiftyOneRobbinsDriveMember
     
Building and Improvements 448us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFiftyOneRobbinsDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 877us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFiftyOneRobbinsDriveMember
     
Land 192us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFiftyOneRobbinsDriveMember
     
Building and improvements 1,229us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFiftyOneRobbinsDriveMember
     
Total 1,421us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFiftyOneRobbinsDriveMember
     
Accumulated depreciation 12/31/2012 1,104us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourHundredFiftyOneRobbinsDriveMember
     
1416 Meijer Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 94us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredSixteenMeijerDriveMember
     
Building and Improvements 394us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredSixteenMeijerDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 399us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredSixteenMeijerDriveMember
     
Land 121us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredSixteenMeijerDriveMember
     
Building and improvements 766us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredSixteenMeijerDriveMember
     
Total 887us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredSixteenMeijerDriveMember
     
Accumulated depreciation 12/31/2012 701us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandFourHundredSixteenMeijerDriveMember
     
1624 Meijer Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 236us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredTwentyFourMeijerDriveMember
     
Building and Improvements 1,406us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredTwentyFourMeijerDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,093us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredTwentyFourMeijerDriveMember
     
Land 373us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredTwentyFourMeijerDriveMember
     
Building and improvements 2,362us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredTwentyFourMeijerDriveMember
     
Total 2,735us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredTwentyFourMeijerDriveMember
     
Accumulated depreciation 12/31/2012 1,999us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSixHundredTwentyFourMeijerDriveMember
     
1972 Meijer Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 315us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandNineHundredSeventyTwoMeijerDriveMember
     
Building and Improvements 1,301us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandNineHundredSeventyTwoMeijerDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 787us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandNineHundredSeventyTwoMeijerDriveMember
     
Land 372us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandNineHundredSeventyTwoMeijerDriveMember
     
Building and improvements 2,031us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandNineHundredSeventyTwoMeijerDriveMember
     
Total 2,403us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandNineHundredSeventyTwoMeijerDriveMember
     
Accumulated depreciation 12/31/2012 1,555us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandNineHundredSeventyTwoMeijerDriveMember
     
1707 Northwood Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 95us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredSevenNorthwoodDriveMember
     
Building and Improvements 262us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredSevenNorthwoodDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,720us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredSevenNorthwoodDriveMember
     
Land 239us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredSevenNorthwoodDriveMember
     
Building and improvements 1,838us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredSevenNorthwoodDriveMember
     
Total 2,077us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredSevenNorthwoodDriveMember
     
Accumulated depreciation 12/31/2012 1,446us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThousandSevenHundredSevenNorthwoodDriveMember
     
1788 Northwood Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 50us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightEightNorthwoodDriveMember
     
Building and Improvements 196us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightEightNorthwoodDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 483us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightEightNorthwoodDriveMember
     
Land 103us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightEightNorthwoodDriveMember
     
Building and improvements 626us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightEightNorthwoodDriveMember
     
Total 729us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightEightNorthwoodDriveMember
     
Accumulated depreciation 12/31/2012 566us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightEightNorthwoodDriveMember
     
1826 Northwood Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 55us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoSixNorthwoodDriveMember
     
Building and Improvements 208us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoSixNorthwoodDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 472us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoSixNorthwoodDriveMember
     
Land 103us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoSixNorthwoodDriveMember
     
Building and improvements 632us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoSixNorthwoodDriveMember
     
Total 735us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoSixNorthwoodDriveMember
     
Accumulated depreciation 12/31/2012 557us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoSixNorthwoodDriveMember
     
1864 Northwood Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 57us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourNorthwoodDriveMember
     
Building and Improvements 190us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourNorthwoodDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 489us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourNorthwoodDriveMember
     
Land 107us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourNorthwoodDriveMember
     
Building and improvements 629us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourNorthwoodDriveMember
     
Total 736us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourNorthwoodDriveMember
     
Accumulated depreciation 12/31/2012 573us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourNorthwoodDriveMember
     
2451 Elliott Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 78us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveOneElliottAvenueMember
     
Building and Improvements 319us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveOneElliottAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 733us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveOneElliottAvenueMember
     
Land 164us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveOneElliottAvenueMember
     
Building and improvements 966us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveOneElliottAvenueMember
     
Total 1,130us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveOneElliottAvenueMember
     
Accumulated depreciation 12/31/2012 786us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveOneElliottAvenueMember
     
2730 Research Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 903us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenThreeZeroResearchDriveMember
     
Building and Improvements 4,215us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenThreeZeroResearchDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 829us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenThreeZeroResearchDriveMember
     
Land 903us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenThreeZeroResearchDriveMember
     
Building and improvements 5,044us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenThreeZeroResearchDriveMember
     
Total 5,947us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenThreeZeroResearchDriveMember
     
Accumulated depreciation 12/31/2012 4,093us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenThreeZeroResearchDriveMember
     
2791 Research Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 557us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenNineOneResearchDriveMember
     
Building and Improvements 2,731us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenNineOneResearchDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,017us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenNineOneResearchDriveMember
     
Land 560us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenNineOneResearchDriveMember
     
Building and improvements 3,745us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenNineOneResearchDriveMember
     
Total 4,305us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenNineOneResearchDriveMember
     
Accumulated depreciation 12/31/2012 2,552us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenNineOneResearchDriveMember
     
2871 Research Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 324us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenOneResearchDriveMember
     
Building and Improvements 1,487us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenOneResearchDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 437us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenOneResearchDriveMember
     
Land 327us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenOneResearchDriveMember
     
Building and improvements 1,921us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenOneResearchDriveMember
     
Total 2,248us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenOneResearchDriveMember
     
Accumulated depreciation 12/31/2012 1,420us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenOneResearchDriveMember
     
3011 Research Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 457us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneOneResearchDriveMember
     
Building and Improvements 2,104us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneOneResearchDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 492us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneOneResearchDriveMember
     
Land 457us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneOneResearchDriveMember
     
Building and improvements 2,596us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneOneResearchDriveMember
     
Total 3,053us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneOneResearchDriveMember
     
Accumulated depreciation 12/31/2012 2,091us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneOneResearchDriveMember
     
2870 Technology Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 275us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenZeroTechnologyDriveMember
     
Building and Improvements 1,262us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenZeroTechnologyDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 356us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenZeroTechnologyDriveMember
     
Land 279us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenZeroTechnologyDriveMember
     
Building and improvements 1,614us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenZeroTechnologyDriveMember
     
Total 1,893us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenZeroTechnologyDriveMember
     
Accumulated depreciation 12/31/2012 1,278us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightSevenZeroTechnologyDriveMember
     
2900 Technology Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 214us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroTechnologyDriveMember
     
Building and Improvements 977us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroTechnologyDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 513us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroTechnologyDriveMember
     
Land 219us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroTechnologyDriveMember
     
Building and improvements 1,485us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroTechnologyDriveMember
     
Total 1,704us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroTechnologyDriveMember
     
Accumulated depreciation 12/31/2012 971us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroTechnologyDriveMember
     
2930 Technology Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 131us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineThreeZeroTechnologyDriveMember
     
Building and Improvements 594us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineThreeZeroTechnologyDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 435us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineThreeZeroTechnologyDriveMember
     
Land 138us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineThreeZeroTechnologyDriveMember
     
Building and improvements 1,022us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineThreeZeroTechnologyDriveMember
     
Total 1,160us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineThreeZeroTechnologyDriveMember
     
Accumulated depreciation 12/31/2012 698us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineThreeZeroTechnologyDriveMember
     
2950 Technology Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 178us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineFiveZeroTechnologyDriveMember
     
Building and Improvements 819us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineFiveZeroTechnologyDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 368us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineFiveZeroTechnologyDriveMember
     
Land 185us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineFiveZeroTechnologyDriveMember
     
Building and improvements 1,180us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineFiveZeroTechnologyDriveMember
     
Total 1,365us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineFiveZeroTechnologyDriveMember
     
Accumulated depreciation 12/31/2012 801us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineFiveZeroTechnologyDriveMember
     
23014 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 39us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroOneFourCommerceDriveMember
     
Building and Improvements 203us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroOneFourCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 189us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroOneFourCommerceDriveMember
     
Land 56us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroOneFourCommerceDriveMember
     
Building and improvements 375us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroOneFourCommerceDriveMember
     
Total 431us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroOneFourCommerceDriveMember
     
Accumulated depreciation 12/31/2012 333us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroOneFourCommerceDriveMember
     
23028 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 98us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroTwoEightCommerceDriveMember
     
Building and Improvements 507us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroTwoEightCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 278us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroTwoEightCommerceDriveMember
     
Land 125us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroTwoEightCommerceDriveMember
     
Building and improvements 758us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroTwoEightCommerceDriveMember
     
Total 883us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroTwoEightCommerceDriveMember
     
Accumulated depreciation 12/31/2012 704us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroTwoEightCommerceDriveMember
     
23035 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 71us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroThreeFiveCommerceDriveMember
     
Building and Improvements 355us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroThreeFiveCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 237us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroThreeFiveCommerceDriveMember
     
Land 93us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroThreeFiveCommerceDriveMember
     
Building and improvements 570us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroThreeFiveCommerceDriveMember
     
Total 663us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroThreeFiveCommerceDriveMember
     
Accumulated depreciation 12/31/2012 526us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroThreeFiveCommerceDriveMember
     
23042 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 67us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroFourTwoCommerceDriveMember
     
Building and Improvements 277us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroFourTwoCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 273us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroFourTwoCommerceDriveMember
     
Land 89us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroFourTwoCommerceDriveMember
     
Building and improvements 528us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroFourTwoCommerceDriveMember
     
Total 617us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroFourTwoCommerceDriveMember
     
Accumulated depreciation 12/31/2012 500us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroFourTwoCommerceDriveMember
     
23065 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 71us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSixFiveCommerceDriveMember
     
Building and Improvements 408us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSixFiveCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 338us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSixFiveCommerceDriveMember
     
Land 93us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSixFiveCommerceDriveMember
     
Building and improvements 724us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSixFiveCommerceDriveMember
     
Total 817us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSixFiveCommerceDriveMember
     
Accumulated depreciation 12/31/2012 599us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSixFiveCommerceDriveMember
     
23079 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 68us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSevenNineCommerceDriveMember
     
Building and Improvements 301us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSevenNineCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 290us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSevenNineCommerceDriveMember
     
Land 79us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSevenNineCommerceDriveMember
     
Building and improvements 580us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSevenNineCommerceDriveMember
     
Total 659us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSevenNineCommerceDriveMember
     
Accumulated depreciation 12/31/2012 524us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroSevenNineCommerceDriveMember
     
23093 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 211us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroNineThreeCommerceDriveMember
     
Building and Improvements 1,024us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroNineThreeCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,219us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroNineThreeCommerceDriveMember
     
Land 295us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroNineThreeCommerceDriveMember
     
Building and improvements 2,159us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroNineThreeCommerceDriveMember
     
Total 2,454us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroNineThreeCommerceDriveMember
     
Accumulated depreciation 12/31/2012 1,758us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroNineThreeCommerceDriveMember
     
23135 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 146us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneThreeFiveCommerceDriveMember
     
Building and Improvements 701us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneThreeFiveCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 392us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneThreeFiveCommerceDriveMember
     
Land 158us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneThreeFiveCommerceDriveMember
     
Building and improvements 1,081us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneThreeFiveCommerceDriveMember
     
Total 1,239us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneThreeFiveCommerceDriveMember
     
Accumulated depreciation 12/31/2012 904us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneThreeFiveCommerceDriveMember
     
23163 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 111us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSixThreeCommerceDriveMember
     
Building and Improvements 513us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSixThreeCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 384us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSixThreeCommerceDriveMember
     
Land 138us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSixThreeCommerceDriveMember
     
Building and improvements 870us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSixThreeCommerceDriveMember
     
Total 1,008us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSixThreeCommerceDriveMember
     
Accumulated depreciation 12/31/2012 729us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSixThreeCommerceDriveMember
     
23177 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 175us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSevenSevenCommerceDriveMember
     
Building and Improvements 1,007us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSevenSevenCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 611us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSevenSevenCommerceDriveMember
     
Land 254us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSevenSevenCommerceDriveMember
     
Building and improvements 1,539us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSevenSevenCommerceDriveMember
     
Total 1,793us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSevenSevenCommerceDriveMember
     
Accumulated depreciation 12/31/2012 1,313us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeOneSevenSevenCommerceDriveMember
     
23206 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 125us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoZeroSixCommerceDriveMember
     
Building and Improvements 531us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoZeroSixCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 367us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoZeroSixCommerceDriveMember
     
Land 137us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoZeroSixCommerceDriveMember
     
Building and improvements 886us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoZeroSixCommerceDriveMember
     
Total 1,023us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoZeroSixCommerceDriveMember
     
Accumulated depreciation 12/31/2012 730us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoZeroSixCommerceDriveMember
     
23370 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Farmington Hills, MI      
Initial Cost of Land 59us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeSevenZeroCommerceDriveMember
     
Building and Improvements 233us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeSevenZeroCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 174us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeSevenZeroCommerceDriveMember
     
Land 66us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeSevenZeroCommerceDriveMember
     
Building and improvements 400us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeSevenZeroCommerceDriveMember
     
Total 466us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeSevenZeroCommerceDriveMember
     
Accumulated depreciation 12/31/2012 374us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeSevenZeroCommerceDriveMember
     
1451 East Lincoln Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Madison Heights, MI      
Initial Cost of Land 299us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEastLincolnAvenueMember
     
Building and Improvements 1,703us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEastLincolnAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (179)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEastLincolnAvenueMember
     
Land 148us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEastLincolnAvenueMember
     
Building and improvements 1,675us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEastLincolnAvenueMember
     
Total 1,823us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEastLincolnAvenueMember
     
Accumulated depreciation 12/31/2012 864us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEastLincolnAvenueMember
     
4400 Purks Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Auburn Hills, MI      
Initial Cost of Land 602us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFourZeroZeroPurksDriveMember
     
Building and Improvements 3,410us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFourZeroZeroPurksDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,300us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFourZeroZeroPurksDriveMember
     
Land 612us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFourZeroZeroPurksDriveMember
     
Building and improvements 6,700us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFourZeroZeroPurksDriveMember
     
Total 7,312us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFourZeroZeroPurksDriveMember
     
Accumulated depreciation 12/31/2012 3,042us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFourZeroZeroPurksDriveMember
     
32450 N Avis Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Madison Heights, MI      
Initial Cost of Land 281us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourFiveZeroNAvisDriveMember
     
Building and Improvements 1,590us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourFiveZeroNAvisDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 541us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourFiveZeroNAvisDriveMember
     
Land 286us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourFiveZeroNAvisDriveMember
     
Building and improvements 2,126us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourFiveZeroNAvisDriveMember
     
Total 2,412us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourFiveZeroNAvisDriveMember
     
Accumulated depreciation 12/31/2012 1,047us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourFiveZeroNAvisDriveMember
     
12707 Eckles Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Plymouth Township, MI      
Initial Cost of Land 255us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroSevenEcklesRoadMember
     
Building and Improvements 1,445us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroSevenEcklesRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 220us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroSevenEcklesRoadMember
     
Land 267us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroSevenEcklesRoadMember
     
Building and improvements 1,653us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroSevenEcklesRoadMember
     
Total 1,920us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroSevenEcklesRoadMember
     
Accumulated depreciation 12/31/2012 729us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroSevenEcklesRoadMember
     
9300-9328 Harrison Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 147us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroZeroNineThreeTwoEightHarrisonRdMember
     
Building and Improvements 834us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroZeroNineThreeTwoEightHarrisonRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 407us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroZeroNineThreeTwoEightHarrisonRdMember
     
Land 159us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroZeroNineThreeTwoEightHarrisonRdMember
     
Building and improvements 1,229us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroZeroNineThreeTwoEightHarrisonRdMember
     
Total 1,388us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroZeroNineThreeTwoEightHarrisonRdMember
     
Accumulated depreciation 12/31/2012 541us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroZeroNineThreeTwoEightHarrisonRdMember
     
9330-9358 Harrison Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 81us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeThreeZeroNineThreeFiveEightHarrisonRdMember
     
Building and Improvements 456us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeThreeZeroNineThreeFiveEightHarrisonRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 255us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeThreeZeroNineThreeFiveEightHarrisonRdMember
     
Land 89us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeThreeZeroNineThreeFiveEightHarrisonRdMember
     
Building and improvements 703us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeThreeZeroNineThreeFiveEightHarrisonRdMember
     
Total 792us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeThreeZeroNineThreeFiveEightHarrisonRdMember
     
Accumulated depreciation 12/31/2012 287us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeThreeZeroNineThreeFiveEightHarrisonRdMember
     
28420-28448 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 143us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoZeroTwoEightFourFourEightHighlandRdMember
     
Building and Improvements 809us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoZeroTwoEightFourFourEightHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 753us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoZeroTwoEightFourFourEightHighlandRdMember
     
Land 154us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoZeroTwoEightFourFourEightHighlandRdMember
     
Building and improvements 1,551us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoZeroTwoEightFourFourEightHighlandRdMember
     
Total 1,705us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoZeroTwoEightFourFourEightHighlandRdMember
     
Accumulated depreciation 12/31/2012 529us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoZeroTwoEightFourFourEightHighlandRdMember
     
28450-28478 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 81us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveZeroTwoEightFourSevenEightHighlandRdMember
     
Building and Improvements 461us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveZeroTwoEightFourSevenEightHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 457us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveZeroTwoEightFourSevenEightHighlandRdMember
     
Land 90us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveZeroTwoEightFourSevenEightHighlandRdMember
     
Building and improvements 909us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveZeroTwoEightFourSevenEightHighlandRdMember
     
Total 999us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveZeroTwoEightFourSevenEightHighlandRdMember
     
Accumulated depreciation 12/31/2012 343us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveZeroTwoEightFourSevenEightHighlandRdMember
     
28421-28449 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 109us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoOneTwoEightFourFourNineHighlandRdMember
     
Building and Improvements 617us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoOneTwoEightFourFourNineHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 473us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoOneTwoEightFourFourNineHighlandRdMember
     
Land 119us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoOneTwoEightFourFourNineHighlandRdMember
     
Building and improvements 1,080us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoOneTwoEightFourFourNineHighlandRdMember
     
Total 1,199us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoOneTwoEightFourFourNineHighlandRdMember
     
Accumulated depreciation 12/31/2012 451us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourTwoOneTwoEightFourFourNineHighlandRdMember
     
28451-28479 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 107us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveOneTwoEightFourSevenNineHighlandRdMember
     
Building and Improvements 608us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveOneTwoEightFourSevenNineHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 411us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveOneTwoEightFourSevenNineHighlandRdMember
     
Land 117us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveOneTwoEightFourSevenNineHighlandRdMember
     
Building and improvements 1,009us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveOneTwoEightFourSevenNineHighlandRdMember
     
Total 1,126us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveOneTwoEightFourSevenNineHighlandRdMember
     
Accumulated depreciation 12/31/2012 396us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourFiveOneTwoEightFourSevenNineHighlandRdMember
     
28825-28909 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 70us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFiveTwoEightNineZeroNineHighlandRdMember
     
Building and Improvements 395us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFiveTwoEightNineZeroNineHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 396us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFiveTwoEightNineZeroNineHighlandRdMember
     
Land 78us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFiveTwoEightNineZeroNineHighlandRdMember
     
Building and improvements 783us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFiveTwoEightNineZeroNineHighlandRdMember
     
Total 861us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFiveTwoEightNineZeroNineHighlandRdMember
     
Accumulated depreciation 12/31/2012 307us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFiveTwoEightNineZeroNineHighlandRdMember
     
28933-29017 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 112us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeThreeTwoNineZeroOneSevenHighlandRdMember
     
Building and Improvements 634us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeThreeTwoNineZeroOneSevenHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 599us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeThreeTwoNineZeroOneSevenHighlandRdMember
     
Land 122us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeThreeTwoNineZeroOneSevenHighlandRdMember
     
Building and improvements 1,223us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeThreeTwoNineZeroOneSevenHighlandRdMember
     
Total 1,345us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeThreeTwoNineZeroOneSevenHighlandRdMember
     
Accumulated depreciation 12/31/2012 434us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeThreeTwoNineZeroOneSevenHighlandRdMember
     
28824-28908 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 134us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFourTwoEightNineZeroEightHighlandRdMember
     
Building and Improvements 760us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFourTwoEightNineZeroEightHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 577us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFourTwoEightNineZeroEightHighlandRdMember
     
Land 145us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFourTwoEightNineZeroEightHighlandRdMember
     
Building and improvements 1,326us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFourTwoEightNineZeroEightHighlandRdMember
     
Total 1,471us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFourTwoEightNineZeroEightHighlandRdMember
     
Accumulated depreciation 12/31/2012 525us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightEightTwoFourTwoEightNineZeroEightHighlandRdMember
     
28932-29016 Highland Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 123us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeTwoTwoNineZeroOneSixHighlandRdMember
     
Building and Improvements 694us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeTwoTwoNineZeroOneSixHighlandRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 582us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeTwoTwoNineZeroOneSixHighlandRdMember
     
Land 133us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeTwoTwoNineZeroOneSixHighlandRdMember
     
Building and improvements 1,266us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeTwoTwoNineZeroOneSixHighlandRdMember
     
Total 1,399us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeTwoTwoNineZeroOneSixHighlandRdMember
     
Accumulated depreciation 12/31/2012 486us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightNineThreeTwoTwoNineZeroOneSixHighlandRdMember
     
9710-9734 Harrison Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 125us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenOneZeroNineSevenThreeFourHarrisonRdMember
     
Building and Improvements 706us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenOneZeroNineSevenThreeFourHarrisonRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 432us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenOneZeroNineSevenThreeFourHarrisonRdMember
     
Land 135us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenOneZeroNineSevenThreeFourHarrisonRdMember
     
Building and improvements 1,128us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenOneZeroNineSevenThreeFourHarrisonRdMember
     
Total 1,263us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenOneZeroNineSevenThreeFourHarrisonRdMember
     
Accumulated depreciation 12/31/2012 474us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenOneZeroNineSevenThreeFourHarrisonRdMember
     
Nine Seven Four Zero Nine Seven Seven Two Harrison Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 132us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenFourZeroNineSevenSevenTwoHarrisonRdMember
     
Building and Improvements 749us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenFourZeroNineSevenSevenTwoHarrisonRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 401us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenFourZeroNineSevenSevenTwoHarrisonRdMember
     
Land 143us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenFourZeroNineSevenSevenTwoHarrisonRdMember
     
Building and improvements 1,139us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenFourZeroNineSevenSevenTwoHarrisonRdMember
     
Total 1,282us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenFourZeroNineSevenSevenTwoHarrisonRdMember
     
Accumulated depreciation 12/31/2012 492us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenFourZeroNineSevenSevenTwoHarrisonRdMember
     
9840-9868 Harrison Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 144us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightFourZeroNineEightSixEightHarrisonRdMember
     
Building and Improvements 815us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightFourZeroNineEightSixEightHarrisonRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 296us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightFourZeroNineEightSixEightHarrisonRdMember
     
Land 155us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightFourZeroNineEightSixEightHarrisonRdMember
     
Building and improvements 1,100us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightFourZeroNineEightSixEightHarrisonRdMember
     
Total 1,255us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightFourZeroNineEightSixEightHarrisonRdMember
     
Accumulated depreciation 12/31/2012 452us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightFourZeroNineEightSixEightHarrisonRdMember
     
9800-9824 Harrison Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 117us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroZeroNineEightTwoFourHarrisonRdMember
     
Building and Improvements 664us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroZeroNineEightTwoFourHarrisonRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 362us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroZeroNineEightTwoFourHarrisonRdMember
     
Land 127us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroZeroNineEightTwoFourHarrisonRdMember
     
Building and improvements 1,016us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroZeroNineEightTwoFourHarrisonRdMember
     
Total 1,143us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroZeroNineEightTwoFourHarrisonRdMember
     
Accumulated depreciation 12/31/2012 401us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroZeroNineEightTwoFourHarrisonRdMember
     
29265-29285 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 140us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoSixFiveTwoNineTwoEightFiveAirportDrMember
     
Building and Improvements 794us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoSixFiveTwoNineTwoEightFiveAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 263us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoSixFiveTwoNineTwoEightFiveAirportDrMember
     
Land 151us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoSixFiveTwoNineTwoEightFiveAirportDrMember
     
Building and improvements 1,046us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoSixFiveTwoNineTwoEightFiveAirportDrMember
     
Total 1,197us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoSixFiveTwoNineTwoEightFiveAirportDrMember
     
Accumulated depreciation 12/31/2012 462us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoSixFiveTwoNineTwoEightFiveAirportDrMember
     
29185-29225 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 140us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneEightFiveTwoNineTwoTwoFiveAirportDrMember
     
Building and Improvements 792us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneEightFiveTwoNineTwoTwoFiveAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 514us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneEightFiveTwoNineTwoTwoFiveAirportDrMember
     
Land 151us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneEightFiveTwoNineTwoTwoFiveAirportDrMember
     
Building and improvements 1,295us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneEightFiveTwoNineTwoTwoFiveAirportDrMember
     
Total 1,446us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneEightFiveTwoNineTwoTwoFiveAirportDrMember
     
Accumulated depreciation 12/31/2012 580us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneEightFiveTwoNineTwoTwoFiveAirportDrMember
     
29149-29165 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 216us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneFourNineTwoNineOneSixFiveAirportDrMember
     
Building and Improvements 1,225us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneFourNineTwoNineOneSixFiveAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 305us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneFourNineTwoNineOneSixFiveAirportDrMember
     
Land 231us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneFourNineTwoNineOneSixFiveAirportDrMember
     
Building and improvements 1,515us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneFourNineTwoNineOneSixFiveAirportDrMember
     
Total 1,746us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneFourNineTwoNineOneSixFiveAirportDrMember
     
Accumulated depreciation 12/31/2012 674us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneFourNineTwoNineOneSixFiveAirportDrMember
     
29101-29115 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 130us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneZeroOneTwoNineOneOneFiveAirportDrMember
     
Building and Improvements 738us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneZeroOneTwoNineOneOneFiveAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 285us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneZeroOneTwoNineOneOneFiveAirportDrMember
     
Land 141us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneZeroOneTwoNineOneOneFiveAirportDrMember
     
Building and improvements 1,012us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneZeroOneTwoNineOneOneFiveAirportDrMember
     
Total 1,153us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneZeroOneTwoNineOneOneFiveAirportDrMember
     
Accumulated depreciation 12/31/2012 472us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneZeroOneTwoNineOneOneFiveAirportDrMember
     
29031-29045 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 124us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroThreeOneTwoNineZeroFourFiveAirportDrMember
     
Building and Improvements 704us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroThreeOneTwoNineZeroFourFiveAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 215us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroThreeOneTwoNineZeroFourFiveAirportDrMember
     
Land 134us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroThreeOneTwoNineZeroFourFiveAirportDrMember
     
Building and improvements 909us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroThreeOneTwoNineZeroFourFiveAirportDrMember
     
Total 1,043us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroThreeOneTwoNineZeroFourFiveAirportDrMember
     
Accumulated depreciation 12/31/2012 374us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroThreeOneTwoNineZeroFourFiveAirportDrMember
     
29050-29062 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 127us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroFiveZeroTwoNineZeroSixTwoAirportDrMember
     
Building and Improvements 718us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroFiveZeroTwoNineZeroSixTwoAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 218us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroFiveZeroTwoNineZeroSixTwoAirportDrMember
     
Land 137us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroFiveZeroTwoNineZeroSixTwoAirportDrMember
     
Building and improvements 926us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroFiveZeroTwoNineZeroSixTwoAirportDrMember
     
Total 1,063us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroFiveZeroTwoNineZeroSixTwoAirportDrMember
     
Accumulated depreciation 12/31/2012 385us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroFiveZeroTwoNineZeroSixTwoAirportDrMember
     
29120-29134 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 161us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneTwoZeroTwoNineOneThreeFourAirportDrMember
     
Building and Improvements 912us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneTwoZeroTwoNineOneThreeFourAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 522us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneTwoZeroTwoNineOneThreeFourAirportDrMember
     
Land 173us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneTwoZeroTwoNineOneThreeFourAirportDrMember
     
Building and improvements 1,422us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneTwoZeroTwoNineOneThreeFourAirportDrMember
     
Total 1,595us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneTwoZeroTwoNineOneThreeFourAirportDrMember
     
Accumulated depreciation 12/31/2012 569us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineOneTwoZeroTwoNineOneThreeFourAirportDrMember
     
29200-29214 Airport Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 170us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoZeroZeroTwoNineTwoOneFourAirportDrMember
     
Building and Improvements 963us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoZeroZeroTwoNineTwoOneFourAirportDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 310us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoZeroZeroTwoNineTwoOneFourAirportDrMember
     
Land 182us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoZeroZeroTwoNineTwoOneFourAirportDrMember
     
Building and improvements 1,261us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoZeroZeroTwoNineTwoOneFourAirportDrMember
     
Total 1,443us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoZeroZeroTwoNineTwoOneFourAirportDrMember
     
Accumulated depreciation 12/31/2012 465us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineTwoZeroZeroTwoNineTwoOneFourAirportDrMember
     
9301-9339 Middlebelt Rd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Romulus, MI      
Initial Cost of Land 124us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroOneNineThreeThreeNineMiddlebeltRdMember
     
Building and Improvements 703us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroOneNineThreeThreeNineMiddlebeltRdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 444us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroOneNineThreeThreeNineMiddlebeltRdMember
     
Land 130us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroOneNineThreeThreeNineMiddlebeltRdMember
     
Building and improvements 1,141us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroOneNineThreeThreeNineMiddlebeltRdMember
     
Total 1,271us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroOneNineThreeThreeNineMiddlebeltRdMember
     
Accumulated depreciation 12/31/2012 510us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeZeroOneNineThreeThreeNineMiddlebeltRdMember
     
32975 Capitol Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 135us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveCapitolAvenueMember
     
Building and Improvements 748us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveCapitolAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (166)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveCapitolAvenueMember
     
Land 77us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveCapitolAvenueMember
     
Building and improvements 640us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveCapitolAvenueMember
     
Total 717us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveCapitolAvenueMember
     
Accumulated depreciation 12/31/2012 313us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveCapitolAvenueMember
     
32920 Capitol Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 76us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineTwoZeroCapitolAvenueMember
     
Building and Improvements 422us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineTwoZeroCapitolAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (62)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineTwoZeroCapitolAvenueMember
     
Land 27us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineTwoZeroCapitolAvenueMember
     
Building and improvements 409us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineTwoZeroCapitolAvenueMember
     
Total 436us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineTwoZeroCapitolAvenueMember
     
Accumulated depreciation 12/31/2012 217us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineTwoZeroCapitolAvenueMember
     
11923 Brookfield Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 120us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneNineTwoThreeBrookfieldAvenueMember
     
Building and Improvements 665us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneNineTwoThreeBrookfieldAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (324)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneNineTwoThreeBrookfieldAvenueMember
     
Land 32us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneNineTwoThreeBrookfieldAvenueMember
     
Building and improvements 429us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneNineTwoThreeBrookfieldAvenueMember
     
Total 461us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneNineTwoThreeBrookfieldAvenueMember
     
Accumulated depreciation 12/31/2012 294us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneNineTwoThreeBrookfieldAvenueMember
     
450 Robbins Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 166us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveZeroRobbinsDriveMember
     
Building and Improvements 920us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveZeroRobbinsDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 231us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveZeroRobbinsDriveMember
     
Land 178us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveZeroRobbinsDriveMember
     
Building and improvements 1,139us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveZeroRobbinsDriveMember
     
Total 1,317us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveZeroRobbinsDriveMember
     
Accumulated depreciation 12/31/2012 467us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveZeroRobbinsDriveMember
     
12886 Westmore Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 190us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightSixWestmoreAvenueMember
     
Building and Improvements 1,050us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightSixWestmoreAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (351)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightSixWestmoreAvenueMember
     
Land 86us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightSixWestmoreAvenueMember
     
Building and improvements 803us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightSixWestmoreAvenueMember
     
Total 889us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightSixWestmoreAvenueMember
     
Accumulated depreciation 12/31/2012 442us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightSixWestmoreAvenueMember
     
47711 Clipper Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Plymouth Township, MI      
Initial Cost of Land 539us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenOneOneClipperStreetMember
     
Building and Improvements 2,983us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenOneOneClipperStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 359us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenOneOneClipperStreetMember
     
Land 575us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenOneOneClipperStreetMember
     
Building and improvements 3,306us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenOneOneClipperStreetMember
     
Total 3,881us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenOneOneClipperStreetMember
     
Accumulated depreciation 12/31/2012 1,338us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenSevenOneOneClipperStreetMember
     
32975 Industrial Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 160us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveIndustrialRoadMember
     
Building and Improvements 887us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveIndustrialRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (191)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveIndustrialRoadMember
     
Land 92us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveIndustrialRoadMember
     
Building and improvements 764us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveIndustrialRoadMember
     
Total 856us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveIndustrialRoadMember
     
Accumulated depreciation 12/31/2012 379us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineSevenFiveIndustrialRoadMember
     
32985 Industrial Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 137us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineEightFiveIndustrialRoadMember
     
Building and Improvements 761us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineEightFiveIndustrialRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (329)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineEightFiveIndustrialRoadMember
     
Land 46us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineEightFiveIndustrialRoadMember
     
Building and improvements 523us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineEightFiveIndustrialRoadMember
     
Total 569us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineEightFiveIndustrialRoadMember
     
Accumulated depreciation 12/31/2012 319us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineEightFiveIndustrialRoadMember
     
32995 Industrial Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 160us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineNineFiveIndustrialRoadMember
     
Building and Improvements 887us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineNineFiveIndustrialRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (409)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineNineFiveIndustrialRoadMember
     
Land 53us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineNineFiveIndustrialRoadMember
     
Building and improvements 585us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineNineFiveIndustrialRoadMember
     
Total 638us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineNineFiveIndustrialRoadMember
     
Accumulated depreciation 12/31/2012 363us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoNineNineFiveIndustrialRoadMember
     
12874 Westmore Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 137us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightSevenFourWestmoreAvenueMember
     
Building and Improvements 761us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightSevenFourWestmoreAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (302)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightSevenFourWestmoreAvenueMember
     
Land 58us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightSevenFourWestmoreAvenueMember
     
Building and improvements 538us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightSevenFourWestmoreAvenueMember
     
Total 596us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightSevenFourWestmoreAvenueMember
     
Accumulated depreciation 12/31/2012 301us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightSevenFourWestmoreAvenueMember
     
1775 Bellingham [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 344us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenSevenFiveBellinghamMember
     
Building and Improvements 1,902us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenSevenFiveBellinghamMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 329us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenSevenFiveBellinghamMember
     
Land 367us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenSevenFiveBellinghamMember
     
Building and improvements 2,208us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenSevenFiveBellinghamMember
     
Total 2,575us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenSevenFiveBellinghamMember
     
Accumulated depreciation 12/31/2012 893us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenSevenFiveBellinghamMember
     
1785 East Maple [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 92us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightFiveEastMapleMember
     
Building and Improvements 507us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightFiveEastMapleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 200us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightFiveEastMapleMember
     
Land 98us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightFiveEastMapleMember
     
Building and improvements 701us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightFiveEastMapleMember
     
Total 799us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightFiveEastMapleMember
     
Accumulated depreciation 12/31/2012 257us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenEightFiveEastMapleMember
     
980 Chicago [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 206us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroChicagoMember
     
Building and Improvements 1,141us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroChicagoMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 328us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroChicagoMember
     
Land 220us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroChicagoMember
     
Building and improvements 1,455us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroChicagoMember
     
Total 1,675us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroChicagoMember
     
Accumulated depreciation 12/31/2012 537us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightZeroChicagoMember
     
1885 Enterprise Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 209us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightEightFiveEnterpriseDriveMember
     
Building and Improvements 1,158us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightEightFiveEnterpriseDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 544us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightEightFiveEnterpriseDriveMember
     
Land 223us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightEightFiveEnterpriseDriveMember
     
Building and improvements 1,688us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightEightFiveEnterpriseDriveMember
     
Total 1,911us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightEightFiveEnterpriseDriveMember
     
Accumulated depreciation 12/31/2012 561us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightEightFiveEnterpriseDriveMember
     
1935-55 Enterprise Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 1,285us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeFiveAndFiveFiveEnterpriseDriveMember
     
Building and Improvements 7,144us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeFiveAndFiveFiveEnterpriseDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 943us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeFiveAndFiveFiveEnterpriseDriveMember
     
Land 1,371us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeFiveAndFiveFiveEnterpriseDriveMember
     
Building and improvements 8,001us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeFiveAndFiveFiveEnterpriseDriveMember
     
Total 9,372us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeFiveAndFiveFiveEnterpriseDriveMember
     
Accumulated depreciation 12/31/2012 3,229us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeFiveAndFiveFiveEnterpriseDriveMember
     
5500 Enterprise Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Warren, MI      
Initial Cost of Land 675us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroZeroEnterpriseCourtMember
     
Building and Improvements 3,737us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroZeroEnterpriseCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 680us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroZeroEnterpriseCourtMember
     
Land 721us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroZeroEnterpriseCourtMember
     
Building and improvements 4,371us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroZeroEnterpriseCourtMember
     
Total 5,092us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroZeroEnterpriseCourtMember
     
Accumulated depreciation 12/31/2012 1,751us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroZeroEnterpriseCourtMember
     
750 Chicago Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 323us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroChicagoRoadMember
     
Building and Improvements 1,790us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroChicagoRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 385us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroChicagoRoadMember
     
Land 345us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroChicagoRoadMember
     
Building and improvements 2,153us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroChicagoRoadMember
     
Total 2,498us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroChicagoRoadMember
     
Accumulated depreciation 12/31/2012 880us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroChicagoRoadMember
     
800 Chicago Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 283us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroZeroChicagoRoadMember
     
Building and Improvements 1,567us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroZeroChicagoRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 370us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroZeroChicagoRoadMember
     
Land 302us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroZeroChicagoRoadMember
     
Building and improvements 1,918us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroZeroChicagoRoadMember
     
Total 2,220us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroZeroChicagoRoadMember
     
Accumulated depreciation 12/31/2012 763us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroZeroChicagoRoadMember
     
850 Chicago Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 183us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroChicagoRoadMember
     
Building and Improvements 1,016us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroChicagoRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 218us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroChicagoRoadMember
     
Land 196us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroChicagoRoadMember
     
Building and improvements 1,221us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroChicagoRoadMember
     
Total 1,417us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroChicagoRoadMember
     
Accumulated depreciation 12/31/2012 493us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroChicagoRoadMember
     
1100 East Mandoline Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Madison Heights, MI      
Initial Cost of Land 888us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneZeroZeroEastMandolineRoadMember
     
Building and Improvements 4,915us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneZeroZeroEastMandolineRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,257)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneZeroZeroEastMandolineRoadMember
     
Land 332us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneZeroZeroEastMandolineRoadMember
     
Building and improvements 4,214us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneZeroZeroEastMandolineRoadMember
     
Total 4,546us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneZeroZeroEastMandolineRoadMember
     
Accumulated depreciation 12/31/2012 2,372us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneZeroZeroEastMandolineRoadMember
     
One Zero Eight Zero One One Two Zero One One Eight Zero John Papalas Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lincoln Park, MI      
Initial Cost of Land 366us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightZeroOneOneTwoZeroOneOneEightZeroJohnPapalasDriveMember
     
Building and Improvements 3,241us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightZeroOneOneTwoZeroOneOneEightZeroJohnPapalasDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 366us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightZeroOneOneTwoZeroOneOneEightZeroJohnPapalasDriveMember
     
Land 297us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightZeroOneOneTwoZeroOneOneEightZeroJohnPapalasDriveMember
     
Building and improvements 3,676us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightZeroOneOneTwoZeroOneOneEightZeroJohnPapalasDriveMember
     
Total 3,973us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightZeroOneOneTwoZeroOneOneEightZeroJohnPapalasDriveMember
     
Accumulated depreciation 12/31/2012 1,918us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightZeroOneOneTwoZeroOneOneEightZeroJohnPapalasDriveMember
     
4872 S. Lapeer Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lake Orion Twsp, MI      
Initial Cost of Land 1,342us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightSevenTwoSLapeerRoadMember
     
Building and Improvements 5,441us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightSevenTwoSLapeerRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,208us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightSevenTwoSLapeerRoadMember
     
Land 1,412us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightSevenTwoSLapeerRoadMember
     
Building and improvements 6,579us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightSevenTwoSLapeerRoadMember
     
Total 7,991us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightSevenTwoSLapeerRoadMember
     
Accumulated depreciation 12/31/2012 2,609us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightSevenTwoSLapeerRoadMember
     
22701 Trolley Industrial [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Taylor, MI      
Initial Cost of Land 795us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoSevenZeroOneTrolleyIndustrialMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 7,435us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoSevenZeroOneTrolleyIndustrialMember
     
Land 849us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoSevenZeroOneTrolleyIndustrialMember
     
Building and improvements 7,381us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoSevenZeroOneTrolleyIndustrialMember
     
Total 8,230us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoSevenZeroOneTrolleyIndustrialMember
     
Accumulated depreciation 12/31/2012 2,475us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoSevenZeroOneTrolleyIndustrialMember
     
1400 Allen Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 209us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroZeroAllenDriveMember
     
Building and Improvements 1,154us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroZeroAllenDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 223us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroZeroAllenDriveMember
     
Land 212us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroZeroAllenDriveMember
     
Building and improvements 1,374us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroZeroAllenDriveMember
     
Total 1,586us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroZeroAllenDriveMember
     
Accumulated depreciation 12/31/2012 455us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroZeroAllenDriveMember
     
1408 Allen Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 151us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroEightAllenDriveMember
     
Building and Improvements 834us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroEightAllenDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 121us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroEightAllenDriveMember
     
Land 153us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroEightAllenDriveMember
     
Building and improvements 953us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroEightAllenDriveMember
     
Total 1,106us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroEightAllenDriveMember
     
Accumulated depreciation 12/31/2012 318us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroEightAllenDriveMember
     
32505 Industrial Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Madison Heights, MI      
Initial Cost of Land 345us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFiveZeroFiveIndustrialDriveMember
     
Building and Improvements 1,910us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFiveZeroFiveIndustrialDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 107us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFiveZeroFiveIndustrialDriveMember
     
Land 351us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFiveZeroFiveIndustrialDriveMember
     
Building and improvements 2,011us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFiveZeroFiveIndustrialDriveMember
     
Total 2,362us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFiveZeroFiveIndustrialDriveMember
     
Accumulated depreciation 12/31/2012 694us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFiveZeroFiveIndustrialDriveMember
     
One Seven Nine Nine to One Eight Five Five Northfield Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rochester Hills, MI      
Initial Cost of Land 481us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenNineNinetoOneEightFiveFiveNorthfieldDriveMember
     
Building and Improvements 2,665us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenNineNinetoOneEightFiveFiveNorthfieldDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 367us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenNineNinetoOneEightFiveFiveNorthfieldDriveMember
     
Land 490us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenNineNinetoOneEightFiveFiveNorthfieldDriveMember
     
Building and improvements 3,023us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenNineNinetoOneEightFiveFiveNorthfieldDriveMember
     
Total 3,513us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenNineNinetoOneEightFiveFiveNorthfieldDriveMember
     
Accumulated depreciation 12/31/2012 1,060us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenNineNinetoOneEightFiveFiveNorthfieldDriveMember
     
28435 Automation Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Wixom, MI      
Initial Cost of Land 621us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourThreeFiveAutomationBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,664us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourThreeFiveAutomationBlvdMember
     
Land 628us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourThreeFiveAutomationBlvdMember
     
Building and improvements 3,657us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourThreeFiveAutomationBlvdMember
     
Total 4,285us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourThreeFiveAutomationBlvdMember
     
Accumulated depreciation 12/31/2012 919us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightFourThreeFiveAutomationBlvdMember
     
32200 N Avis Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Madison Heights, MI      
Initial Cost of Land 503us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoTwoZeroZeroNAvisDriveMember
     
Building and Improvements 3,367us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoTwoZeroZeroNAvisDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,446)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoTwoZeroZeroNAvisDriveMember
     
Land 195us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoTwoZeroZeroNAvisDriveMember
     
Building and improvements 2,229us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoTwoZeroZeroNAvisDriveMember
     
Total 2,424us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoTwoZeroZeroNAvisDriveMember
     
Accumulated depreciation 12/31/2012 867us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoTwoZeroZeroNAvisDriveMember
     
100 Kay Industrial Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Orion Township, MI      
Initial Cost of Land 677us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroKayIndustrialDriveMember
     
Building and Improvements 2,018us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroKayIndustrialDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 171us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroKayIndustrialDriveMember
     
Land 685us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroKayIndustrialDriveMember
     
Building and improvements 2,181us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroKayIndustrialDriveMember
     
Total 2,866us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroKayIndustrialDriveMember
     
Accumulated depreciation 12/31/2012 860us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroKayIndustrialDriveMember
     
11800 Sears Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Livonia, MI      
Initial Cost of Land 693us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneEightZeroZeroSearsDriveMember
     
Building and Improvements 1,507us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneEightZeroZeroSearsDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,212us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneEightZeroZeroSearsDriveMember
     
Land 476us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneEightZeroZeroSearsDriveMember
     
Building and improvements 2,936us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneEightZeroZeroSearsDriveMember
     
Total 3,412us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneEightZeroZeroSearsDriveMember
     
Accumulated depreciation 12/31/2012 1,451us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneEightZeroZeroSearsDriveMember
     
1099 Chicago Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Troy, MI      
Initial Cost of Land 1,277us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineNineChicagoRoadMember
     
Building and Improvements 1,332us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineNineChicagoRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,275)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineNineChicagoRoadMember
     
Land 303us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineNineChicagoRoadMember
     
Building and improvements 1,031us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineNineChicagoRoadMember
     
Total 1,334us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineNineChicagoRoadMember
     
Accumulated depreciation 12/31/2012 294us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineNineChicagoRoadMember
     
42555 Merrill Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Sterling Heights, MI      
Initial Cost of Land 1,080us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveFiveFiveMerrillRoadMember
     
Building and Improvements 2,300us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveFiveFiveMerrillRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,487us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveFiveFiveMerrillRoadMember
     
Land 1,090us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveFiveFiveMerrillRoadMember
     
Building and improvements 5,777us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveFiveFiveMerrillRoadMember
     
Total 6,867us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveFiveFiveMerrillRoadMember
     
Accumulated depreciation 12/31/2012 1,991us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourTwoFiveFiveFiveMerrillRoadMember
     
200 Northpointe Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Orion Township, MI      
Initial Cost of Land 723us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNorthpointeDriveMember
     
Building and Improvements 2,063us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNorthpointeDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 36us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNorthpointeDriveMember
     
Land 734us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNorthpointeDriveMember
     
Building and improvements 2,088us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNorthpointeDriveMember
     
Total 2,822us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNorthpointeDriveMember
     
Accumulated depreciation 12/31/2012 882us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroNorthpointeDriveMember
     
3351 Rauch St [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 272us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeFiveOneRauchStMember
     
Building and Improvements 1,541us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeFiveOneRauchStMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 510us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeFiveOneRauchStMember
     
Land 278us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeFiveOneRauchStMember
     
Building and improvements 2,045us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeFiveOneRauchStMember
     
Total 2,323us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeFiveOneRauchStMember
     
Accumulated depreciation 12/31/2012 764us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeFiveOneRauchStMember
     
3801-3851 Yale St [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   1,977us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
   
Initial Cost of Land 413us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
     
Building and Improvements 2,343us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 419us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
     
Land 425us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
     
Building and improvements 2,750us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
     
Total 3,175us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
     
Accumulated depreciation 12/31/2012 1,158us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightZeroOneToThreeEightFiveOneYaleStMember
     
3337-3347 Rauch Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 227us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeThreeSevenAndThreeThreeFourSevenRauchStreetMember
     
Building and Improvements 1,287us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeThreeSevenAndThreeThreeFourSevenRauchStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 454us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeThreeSevenAndThreeThreeFourSevenRauchStreetMember
     
Land 233us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeThreeSevenAndThreeThreeFourSevenRauchStreetMember
     
Building and improvements 1,735us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeThreeSevenAndThreeThreeFourSevenRauchStreetMember
     
Total 1,968us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeThreeSevenAndThreeThreeFourSevenRauchStreetMember
     
Accumulated depreciation 12/31/2012 669us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeThreeSevenAndThreeThreeFourSevenRauchStreetMember
     
8505 N Loop East [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   1,630us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
   
Initial Cost of Land 439us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
     
Building and Improvements 2,489us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 626us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
     
Land 449us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
     
Building and improvements 3,105us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
     
Total 3,554us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
     
Accumulated depreciation 12/31/2012 1,271us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveZeroFiveNLoopEastMember
     
4749-4799 Eastpark Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   2,409us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
   
Initial Cost of Land 594us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
     
Building and Improvements 3,368us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,290us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
     
Land 611us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
     
Building and improvements 4,641us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
     
Total 5,252us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
     
Accumulated depreciation 12/31/2012 1,898us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourNineAndFourSevenNineNineEastparkDrMember
     
4851 Homestead Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   3,139us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
   
Initial Cost of Land 491us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
     
Building and Improvements 2,782us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,549us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
     
Land 504us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
     
Building and improvements 4,318us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
     
Total 4,822us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
     
Accumulated depreciation 12/31/2012 1,684us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightFiveOneHomesteadRoadMember
     
3365-3385 Rauch Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   1,622us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
   
Initial Cost of Land 284us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
     
Building and Improvements 1,611us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 710us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
     
Land 290us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
     
Building and improvements 2,315us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
     
Total 2,605us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
     
Accumulated depreciation 12/31/2012 1,022us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveAndThreeThreeEightFiveRauchStreetMember
     
5050 Campbell Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   1,871us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
   
Initial Cost of Land 461us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
     
Building and Improvements 2,610us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,009us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
     
Land 470us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
     
Building and improvements 3,610us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
     
Total 4,080us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
     
Accumulated depreciation 12/31/2012 1,316us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroCampbellRoadMember
     
4300 Pine Timbers [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   2,712us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
   
Initial Cost of Land 489us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
     
Building and Improvements 2,769us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 756us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
     
Land 499us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
     
Building and improvements 3,515us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
     
Total 4,014us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
     
Accumulated depreciation 12/31/2012 1,476us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeZeroZeroPineTimbersMember
     
2500-2530 Fairway Park Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   3,287us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
   
Initial Cost of Land 766us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
     
Building and Improvements 4,342us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,059us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
     
Land 792us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
     
Building and improvements 6,375us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
     
Total 7,167us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
     
Accumulated depreciation 12/31/2012 2,419us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroAndTwoFiveThreeZeroFairwayParkDriveMember
     
6550 Longpointe [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   1,567us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
   
Initial Cost of Land 362us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
     
Building and Improvements 2,050us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,004us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
     
Land 370us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
     
Building and improvements 3,046us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
     
Total 3,416us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
     
Accumulated depreciation 12/31/2012 1,092us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveZeroLongpointeMember
     
1815 Turning Basin Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   1,992us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
   
Initial Cost of Land 487us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
     
Building and Improvements 2,761us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,095us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
     
Land 531us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
     
Building and improvements 3,812us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
     
Total 4,343us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
     
Accumulated depreciation 12/31/2012 1,443us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveTurningBasinDrMember
     
1819 Turning Basin Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 231us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneNineTurningBasinDrMember
     
Building and Improvements 1,308us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneNineTurningBasinDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 591us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneNineTurningBasinDrMember
     
Land 251us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneNineTurningBasinDrMember
     
Building and improvements 1,879us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneNineTurningBasinDrMember
     
Total 2,130us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneNineTurningBasinDrMember
     
Accumulated depreciation 12/31/2012 753us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneNineTurningBasinDrMember
     
1805 Turning Basin Dr [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances   2,559us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
   
Initial Cost of Land 564us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
     
Building and Improvements 3,197us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,820us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
     
Land 616us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
     
Building and improvements 4,965us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
     
Total 5,581us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
     
Accumulated depreciation 12/31/2012 1,708us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightZeroFiveTurningBasinDriveMember
     
9835A Genard Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 1,505us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveGenardRoadMember
     
Building and Improvements 8,333us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveGenardRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,257us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveGenardRoadMember
     
Land 1,581us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveGenardRoadMember
     
Building and improvements 11,514us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveGenardRoadMember
     
Total 13,095us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveGenardRoadMember
     
Accumulated depreciation 12/31/2012 3,962us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveGenardRoadMember
     
9835B Genard Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 245us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveBGenardRoadMember
     
Building and Improvements 1,357us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveBGenardRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 663us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveBGenardRoadMember
     
Land 256us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveBGenardRoadMember
     
Building and improvements 2,009us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveBGenardRoadMember
     
Total 2,265us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveBGenardRoadMember
     
Accumulated depreciation 12/31/2012 690us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineEightThreeFiveBGenardRoadMember
     
11505 State Highway 225 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) LaPorte City, TX      
Initial Cost of Land 940us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveZeroFiveStateHighwayTwoTwoFiveMember
     
Building and Improvements 4,675us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveZeroFiveStateHighwayTwoTwoFiveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 606us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveZeroFiveStateHighwayTwoTwoFiveMember
     
Land 940us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveZeroFiveStateHighwayTwoTwoFiveMember
     
Building and improvements 5,281us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveZeroFiveStateHighwayTwoTwoFiveMember
     
Total 6,221us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveZeroFiveStateHighwayTwoTwoFiveMember
     
Accumulated depreciation 12/31/2012 1,847us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveZeroFiveStateHighwayTwoTwoFiveMember
     
1500 E. Main Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 201us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroEMainStreetMember
     
Building and Improvements 1,328us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroEMainStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (26)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroEMainStreetMember
     
Land 204us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroEMainStreetMember
     
Building and improvements 1,299us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroEMainStreetMember
     
Total 1,503us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroEMainStreetMember
     
Accumulated depreciation 12/31/2012 858us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroEMainStreetMember
     
7230-7238 Wynnwood [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 254us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoThreeZeroToSevenTwoThreeEightWynnwoodMember
     
Building and Improvements 764us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoThreeZeroToSevenTwoThreeEightWynnwoodMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 173us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoThreeZeroToSevenTwoThreeEightWynnwoodMember
     
Land 259us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoThreeZeroToSevenTwoThreeEightWynnwoodMember
     
Building and improvements 932us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoThreeZeroToSevenTwoThreeEightWynnwoodMember
     
Total 1,191us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoThreeZeroToSevenTwoThreeEightWynnwoodMember
     
Accumulated depreciation 12/31/2012 349us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoThreeZeroToSevenTwoThreeEightWynnwoodMember
     
7240-7248 Wynnwood [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 271us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFourZeroToSevenTwoFourEightWynnwoodMember
     
Building and Improvements 726us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFourZeroToSevenTwoFourEightWynnwoodMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 35us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFourZeroToSevenTwoFourEightWynnwoodMember
     
Land 276us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFourZeroToSevenTwoFourEightWynnwoodMember
     
Building and improvements 756us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFourZeroToSevenTwoFourEightWynnwoodMember
     
Total 1,032us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFourZeroToSevenTwoFourEightWynnwoodMember
     
Accumulated depreciation 12/31/2012 342us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFourZeroToSevenTwoFourEightWynnwoodMember
     
7250-7260 Wynnwood [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveZeroToSevenTwoSixZeroWynnwoodMember
     
Building and Improvements 481us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveZeroToSevenTwoSixZeroWynnwoodMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 141us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveZeroToSevenTwoSixZeroWynnwoodMember
     
Land 203us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveZeroToSevenTwoSixZeroWynnwoodMember
     
Building and improvements 619us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveZeroToSevenTwoSixZeroWynnwoodMember
     
Total 822us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveZeroToSevenTwoSixZeroWynnwoodMember
     
Accumulated depreciation 12/31/2012 227us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveZeroToSevenTwoSixZeroWynnwoodMember
     
6400 Long Point [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 188us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourZeroZeroLongPointMember
     
Building and Improvements 898us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourZeroZeroLongPointMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (47)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourZeroZeroLongPointMember
     
Land 188us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourZeroZeroLongPointMember
     
Building and improvements 851us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourZeroZeroLongPointMember
     
Total 1,039us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourZeroZeroLongPointMember
     
Accumulated depreciation 12/31/2012 291us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourZeroZeroLongPointMember
     
12705 S. Kirkwood, Ste 100-150 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Stafford, TX      
Initial Cost of Land 154us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteOneZeroZeroToOneFiveZeroMember
     
Building and Improvements 626us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteOneZeroZeroToOneFiveZeroMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 8us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteOneZeroZeroToOneFiveZeroMember
     
Land 155us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteOneZeroZeroToOneFiveZeroMember
     
Building and improvements 633us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteOneZeroZeroToOneFiveZeroMember
     
Total 788us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteOneZeroZeroToOneFiveZeroMember
     
Accumulated depreciation 12/31/2012 166us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteOneZeroZeroToOneFiveZeroMember
     
12705 S. Kirkwood, Ste 200-220 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Stafford, TX      
Initial Cost of Land 404us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteTwoZeroZeroToTwoTwoZeroMember
     
Building and Improvements 1,698us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteTwoZeroZeroToTwoTwoZeroMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 275us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteTwoZeroZeroToTwoTwoZeroMember
     
Land 393us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteTwoZeroZeroToTwoTwoZeroMember
     
Building and improvements 1,984us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteTwoZeroZeroToTwoTwoZeroMember
     
Total 2,377us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteTwoZeroZeroToTwoTwoZeroMember
     
Accumulated depreciation 12/31/2012 747us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroFiveSKirkwoodSteTwoZeroZeroToTwoTwoZeroMember
     
8850 Jameel [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 171us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightFiveZeroJameelMember
     
Building and Improvements 826us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightFiveZeroJameelMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 4us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightFiveZeroJameelMember
     
Land 171us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightFiveZeroJameelMember
     
Building and improvements 830us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightFiveZeroJameelMember
     
Total 1,001us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightFiveZeroJameelMember
     
Accumulated depreciation 12/31/2012 305us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightFiveZeroJameelMember
     
8800 Jameel [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 163us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroJameelMember
     
Building and Improvements 798us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroJameelMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (100)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroJameelMember
     
Land 124us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroJameelMember
     
Building and improvements 737us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroJameelMember
     
Total 861us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroJameelMember
     
Accumulated depreciation 12/31/2012 264us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroJameelMember
     
8700 Jameel [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 170us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenZeroZeroJameelMember
     
Building and Improvements 1,020us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenZeroZeroJameelMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (178)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenZeroZeroJameelMember
     
Land 120us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenZeroZeroJameelMember
     
Building and improvements 892us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenZeroZeroJameelMember
     
Total 1,012us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenZeroZeroJameelMember
     
Accumulated depreciation 12/31/2012 236us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenZeroZeroJameelMember
     
8600 Jameel [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 163us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSixZeroZeroJameelMember
     
Building and Improvements 818us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSixZeroZeroJameelMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 41us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSixZeroZeroJameelMember
     
Land 163us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSixZeroZeroJameelMember
     
Building and improvements 859us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSixZeroZeroJameelMember
     
Total 1,022us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSixZeroZeroJameelMember
     
Accumulated depreciation 12/31/2012 313us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSixZeroZeroJameelMember
     
7967 Blankenship [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 307us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineSixSevenBlankenshipMember
     
Building and Improvements 1,166us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineSixSevenBlankenshipMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 337us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineSixSevenBlankenshipMember
     
Land 307us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineSixSevenBlankenshipMember
     
Building and improvements 1,503us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineSixSevenBlankenshipMember
     
Total 1,810us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineSixSevenBlankenshipMember
     
Accumulated depreciation 12/31/2012 363us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineSixSevenBlankenshipMember
     
8800 City Park Look East [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Encumbrances 23,226us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Initial Cost of Land 3,717us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Building and Improvements 19,237us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (659)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Land 3,717us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Building and improvements 18,578us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Total 22,295us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Accumulated depreciation 12/31/2012 2,726us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightEightZeroZeroCityParkLookEastMember
     
Four Thousand Eight Hundred West Greens Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Houston, TX      
Initial Cost of Land 3,350us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandEightHundredWestGreensRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 12,057us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandEightHundredWestGreensRoadMember
     
Land 3,318us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandEightHundredWestGreensRoadMember
     
Building and improvements 12,089us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandEightHundredWestGreensRoadMember
     
Total 15,407us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandEightHundredWestGreensRoadMember
     
Accumulated depreciation 12/31/2012 75us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandEightHundredWestGreensRoadMember
     
2900 N Shadeland Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 2,057us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroNShadelandAvenueMember
     
Building and Improvements 13,565us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroNShadelandAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,828us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroNShadelandAvenueMember
     
Land 2,057us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroNShadelandAvenueMember
     
Building and improvements 17,393us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroNShadelandAvenueMember
     
Total 19,450us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroNShadelandAvenueMember
     
Accumulated depreciation 12/31/2012 7,484us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoNineZeroZeroNShadelandAvenueMember
     
1445 Brookville Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 459us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourFiveBrookvilleWayMember
     
Building and Improvements 2,603us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourFiveBrookvilleWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,063us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourFiveBrookvilleWayMember
     
Land 476us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourFiveBrookvilleWayMember
     
Building and improvements 3,649us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourFiveBrookvilleWayMember
     
Total 4,125us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourFiveBrookvilleWayMember
     
Accumulated depreciation 12/31/2012 1,548us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourFiveBrookvilleWayMember
     
1440 Brookville Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Encumbrances 3,661us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
Initial Cost of Land 665us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
Building and Improvements 3,770us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 985us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
Land 685us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
Building and improvements 4,735us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
Total 5,420us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
Accumulated depreciation 12/31/2012 2,049us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourZeroBrookvilleWayMember
     
1240 Brookville Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 247us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFourZeroBrookvilleWayMember
     
Building and Improvements 1,402us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFourZeroBrookvilleWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 324us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFourZeroBrookvilleWayMember
     
Land 258us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFourZeroBrookvilleWayMember
     
Building and improvements 1,715us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFourZeroBrookvilleWayMember
     
Total 1,973us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFourZeroBrookvilleWayMember
     
Accumulated depreciation 12/31/2012 776us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFourZeroBrookvilleWayMember
     
1345 Brookville Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 586us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourFiveBrookvilleWayMember
     
Building and Improvements 3,321us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourFiveBrookvilleWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,160us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourFiveBrookvilleWayMember
     
Land 601us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourFiveBrookvilleWayMember
     
Building and improvements 4,466us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourFiveBrookvilleWayMember
     
Total 5,067us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourFiveBrookvilleWayMember
     
Accumulated depreciation 12/31/2012 1,872us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourFiveBrookvilleWayMember
     
1350 Brookville Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 205us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveZeroBrookvilleWayMember
     
Building and Improvements 1,161us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveZeroBrookvilleWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 249us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveZeroBrookvilleWayMember
     
Land 204us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveZeroBrookvilleWayMember
     
Building and improvements 1,411us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveZeroBrookvilleWayMember
     
Total 1,615us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveZeroBrookvilleWayMember
     
Accumulated depreciation 12/31/2012 639us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveZeroBrookvilleWayMember
     
1341 Sadlier Circle South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 131us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourOneSadlierCircleSouthMember
     
Building and Improvements 743us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourOneSadlierCircleSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 205us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourOneSadlierCircleSouthMember
     
Land 136us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourOneSadlierCircleSouthMember
     
Building and improvements 943us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourOneSadlierCircleSouthMember
     
Total 1,079us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourOneSadlierCircleSouthMember
     
Accumulated depreciation 12/31/2012 414us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFourOneSadlierCircleSouthMember
     
1322-1438 Sadlier Circle East [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 145us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoToOneFourThreeEightSadlierCircleEDrMember
     
Building and Improvements 822us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoToOneFourThreeEightSadlierCircleEDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 296us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoToOneFourThreeEightSadlierCircleEDrMember
     
Land 152us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoToOneFourThreeEightSadlierCircleEDrMember
     
Building and improvements 1,111us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoToOneFourThreeEightSadlierCircleEDrMember
     
Total 1,263us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoToOneFourThreeEightSadlierCircleEDrMember
     
Accumulated depreciation 12/31/2012 491us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoTwoToOneFourThreeEightSadlierCircleEDrMember
     
1327-1441 Sadlier Circle West [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 218us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoSevenToOneFourFourOneSadlierCircleEDrMember
     
Building and Improvements 1,234us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoSevenToOneFourFourOneSadlierCircleEDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 607us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoSevenToOneFourFourOneSadlierCircleEDrMember
     
Land 225us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoSevenToOneFourFourOneSadlierCircleEDrMember
     
Building and improvements 1,834us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoSevenToOneFourFourOneSadlierCircleEDrMember
     
Total 2,059us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoSevenToOneFourFourOneSadlierCircleEDrMember
     
Accumulated depreciation 12/31/2012 740us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeTwoSevenToOneFourFourOneSadlierCircleEDrMember
     
1402-1430 Sadlier Circle West [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 165us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroTwoToOneFourThreeZeroSadlierCircleWestMember
     
Building and Improvements 934us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroTwoToOneFourThreeZeroSadlierCircleWestMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 398us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroTwoToOneFourThreeZeroSadlierCircleWestMember
     
Land 171us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroTwoToOneFourThreeZeroSadlierCircleWestMember
     
Building and improvements 1,326us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroTwoToOneFourThreeZeroSadlierCircleWestMember
     
Total 1,497us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroTwoToOneFourThreeZeroSadlierCircleWestMember
     
Accumulated depreciation 12/31/2012 581us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroTwoToOneFourThreeZeroSadlierCircleWestMember
     
1504 Sadlier Circle South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 219us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroFourSadlierCircleEDrMember
     
Building and Improvements 1,238us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroFourSadlierCircleEDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (104)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroFourSadlierCircleEDrMember
     
Land 115us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroFourSadlierCircleEDrMember
     
Building and improvements 1,238us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroFourSadlierCircleEDrMember
     
Total 1,353us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroFourSadlierCircleEDrMember
     
Accumulated depreciation 12/31/2012 746us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroFourSadlierCircleEDrMember
     
1365-1367 Sadlier Way Circle East [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 121us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSixFiveToOneThreeSixSevenSadlierCircleEastMember
     
Building and Improvements 688us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSixFiveToOneThreeSixSevenSadlierCircleEastMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 181us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSixFiveToOneThreeSixSevenSadlierCircleEastMember
     
Land 91us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSixFiveToOneThreeSixSevenSadlierCircleEastMember
     
Building and improvements 899us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSixFiveToOneThreeSixSevenSadlierCircleEastMember
     
Total 990us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSixFiveToOneThreeSixSevenSadlierCircleEastMember
     
Accumulated depreciation 12/31/2012 393us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSixFiveToOneThreeSixSevenSadlierCircleEastMember
     
1352-1354 Sadlier Circle West [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 178us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveTwoToOneThreeFiveFourSadlierCircleEDrMember
     
Building and Improvements 1,008us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveTwoToOneThreeFiveFourSadlierCircleEDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 186us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveTwoToOneThreeFiveFourSadlierCircleEDrMember
     
Land 166us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveTwoToOneThreeFiveFourSadlierCircleEDrMember
     
Building and improvements 1,206us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveTwoToOneThreeFiveFourSadlierCircleEDrMember
     
Total 1,372us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveTwoToOneThreeFiveFourSadlierCircleEDrMember
     
Accumulated depreciation 12/31/2012 541us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeFiveTwoToOneThreeFiveFourSadlierCircleEDrMember
     
1335 Sadlier Circle East [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 81us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeThreeFiveSadlierCircleEDrMember
     
Building and Improvements 460us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeThreeFiveSadlierCircleEDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 202us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeThreeFiveSadlierCircleEDrMember
     
Land 85us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeThreeFiveSadlierCircleEDrMember
     
Building and improvements 658us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeThreeFiveSadlierCircleEDrMember
     
Total 743us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeThreeFiveSadlierCircleEDrMember
     
Accumulated depreciation 12/31/2012 287us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeThreeFiveSadlierCircleEDrMember
     
1425 Sadlier Circle West [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 21us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourTwoFiveSadlierCircleEDrMember
     
Building and Improvements 117us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourTwoFiveSadlierCircleEDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 41us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourTwoFiveSadlierCircleEDrMember
     
Land 23us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourTwoFiveSadlierCircleEDrMember
     
Building and improvements 156us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourTwoFiveSadlierCircleEDrMember
     
Total 179us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourTwoFiveSadlierCircleEDrMember
     
Accumulated depreciation 12/31/2012 67us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourTwoFiveSadlierCircleEDrMember
     
6951 East 30th St [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 256us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneEThreeZeroStreetMember
     
Building and Improvements 1,449us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneEThreeZeroStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 227us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneEThreeZeroStreetMember
     
Land 265us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneEThreeZeroStreetMember
     
Building and improvements 1,667us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneEThreeZeroStreetMember
     
Total 1,932us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneEThreeZeroStreetMember
     
Accumulated depreciation 12/31/2012 754us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneEThreeZeroStreetMember
     
6701 East 30th St [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 78us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenZeroOneEThreeZeroStreetMember
     
Building and Improvements 443us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenZeroOneEThreeZeroStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 98us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenZeroOneEThreeZeroStreetMember
     
Land 82us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenZeroOneEThreeZeroStreetMember
     
Building and improvements 537us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenZeroOneEThreeZeroStreetMember
     
Total 619us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenZeroOneEThreeZeroStreetMember
     
Accumulated depreciation 12/31/2012 247us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenZeroOneEThreeZeroStreetMember
     
6737 East 30th St [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Encumbrances 1,722us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
Initial Cost of Land 385us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
Building and Improvements 2,181us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 222us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
Land 398us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
Building and improvements 2,390us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
Total 2,788us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
Accumulated depreciation 12/31/2012 1,098us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenThreeSevenEThreeZeroStreetMember
     
6555 East 30th St [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 484us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveFiveEThreeZeroStreetMember
     
Building and Improvements 4,760us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveFiveEThreeZeroStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,065us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveFiveEThreeZeroStreetMember
     
Land 484us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveFiveEThreeZeroStreetMember
     
Building and improvements 6,825us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveFiveEThreeZeroStreetMember
     
Total 7,309us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveFiveEThreeZeroStreetMember
     
Accumulated depreciation 12/31/2012 2,870us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveFiveFiveEThreeZeroStreetMember
     
7901 West 21st St. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Encumbrances 4,946us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
Initial Cost of Land 1,048us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
Building and Improvements 6,027us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 246us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
Land 1,048us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
Building and improvements 6,273us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
Total 7,321us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
Accumulated depreciation 12/31/2012 2,725us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenNineZeroOneWestTwentyOneStMember
     
1225 Brookville Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 60us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoTwoFiveBrookvilleWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 417us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoTwoFiveBrookvilleWayMember
     
Land 68us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoTwoFiveBrookvilleWayMember
     
Building and improvements 409us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoTwoFiveBrookvilleWayMember
     
Total 477us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoTwoFiveBrookvilleWayMember
     
Accumulated depreciation 12/31/2012 172us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoTwoFiveBrookvilleWayMember
     
6751 E 30th St [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Encumbrances 2,420us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
Initial Cost of Land 728us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
Building and Improvements 2,837us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 354us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
Land 741us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
Building and improvements 3,178us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
Total 3,919us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
Accumulated depreciation 12/31/2012 1,301us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSevenFiveOneEThirtyStMember
     
6575 East 30th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Encumbrances 1,814us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveSevenFiveEastThreeZeroStreetMember
     
Initial Cost of Land 118us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveSevenFiveEastThreeZeroStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,068us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveSevenFiveEastThreeZeroStreetMember
     
Land 128us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveSevenFiveEastThreeZeroStreetMember
     
Building and improvements 2,058us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveSevenFiveEastThreeZeroStreetMember
     
Total 2,186us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveSevenFiveEastThreeZeroStreetMember
     
Accumulated depreciation 12/31/2012 880us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveSevenFiveEastThreeZeroStreetMember
     
6585 East 30th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Encumbrances 2,814us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveEightFiveEastThreeZeroStreetMember
     
Initial Cost of Land 196us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveEightFiveEastThreeZeroStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,195us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveEightFiveEastThreeZeroStreetMember
     
Land 196us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveEightFiveEastThreeZeroStreetMember
     
Building and improvements 3,195us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveEightFiveEastThreeZeroStreetMember
     
Total 3,391us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveEightFiveEastThreeZeroStreetMember
     
Accumulated depreciation 12/31/2012 1,278us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFiveEightFiveEastThreeZeroStreetMember
     
5705-97 Park Plaza Ct. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Encumbrances 2,464us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
Building and Improvements 2,194us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 853us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
Land 609us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
Building and improvements 3,038us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
Total 3,647us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
Accumulated depreciation 12/31/2012 1,070us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroFiveToNineSevenParkPlazaCourtMember
     
9319-9341 Castlegate Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Indianapolis, IN      
Initial Cost of Land 530us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeOneNineToNineThreeFourOneCastlegateDriveMember
     
Building and Improvements 1,235us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeOneNineToNineThreeFourOneCastlegateDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 688us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeOneNineToNineThreeFourOneCastlegateDriveMember
     
Land 544us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeOneNineToNineThreeFourOneCastlegateDriveMember
     
Building and improvements 1,909us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeOneNineToNineThreeFourOneCastlegateDriveMember
     
Total 2,453us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeOneNineToNineThreeFourOneCastlegateDriveMember
     
Accumulated depreciation 12/31/2012 652us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineThreeOneNineToNineThreeFourOneCastlegateDriveMember
     
1133 Northwest L Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richmond, IN      
Initial Cost of Land 201us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeThreeNorthwestLStreetMember
     
Building and Improvements 1,358us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeThreeNorthwestLStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (188)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeThreeNorthwestLStreetMember
     
Land 208us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeThreeNorthwestLStreetMember
     
Building and improvements 1,163us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeThreeNorthwestLStreetMember
     
Total 1,371us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeThreeNorthwestLStreetMember
     
Accumulated depreciation 12/31/2012 636us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeThreeNorthwestLStreetMember
     
14425 Bergen Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Noblesville, IN      
Initial Cost of Land 647us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourTwoFiveBergenBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,484us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourTwoFiveBergenBlvdMember
     
Land 743us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourTwoFiveBergenBlvdMember
     
Building and improvements 3,388us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourTwoFiveBergenBlvdMember
     
Total 4,131us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourTwoFiveBergenBlvdMember
     
Accumulated depreciation 12/31/2012 615us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFourTwoFiveBergenBlvdMember
     
4700 NW 15th Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ft. Lauderdale, FL      
Initial Cost of Land 908us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroZeroNwOneFiveAvenueMember
     
Building and Improvements 1,883us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroZeroNwOneFiveAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 269us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroZeroNwOneFiveAvenueMember
     
Land 912us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroZeroNwOneFiveAvenueMember
     
Building and improvements 2,148us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroZeroNwOneFiveAvenueMember
     
Total 3,060us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroZeroNwOneFiveAvenueMember
     
Accumulated depreciation 12/31/2012 777us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroZeroNwOneFiveAvenueMember
     
4710 NW 15th Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ft. Lauderdale, FL      
Initial Cost of Land 830us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenOneZeroNwOneFiveAvenueMember
     
Building and Improvements 2,722us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenOneZeroNwOneFiveAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 346us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenOneZeroNwOneFiveAvenueMember
     
Land 834us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenOneZeroNwOneFiveAvenueMember
     
Building and improvements 3,064us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenOneZeroNwOneFiveAvenueMember
     
Total 3,898us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenOneZeroNwOneFiveAvenueMember
     
Accumulated depreciation 12/31/2012 856us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenOneZeroNwOneFiveAvenueMember
     
4720 NW 15th Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ft. Lauderdale, FL      
Initial Cost of Land 937us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoZeroNwOneFiveAvenueMember
     
Building and Improvements 2,455us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoZeroNwOneFiveAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 404us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoZeroNwOneFiveAvenueMember
     
Land 942us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoZeroNwOneFiveAvenueMember
     
Building and improvements 2,854us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoZeroNwOneFiveAvenueMember
     
Total 3,796us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoZeroNwOneFiveAvenueMember
     
Accumulated depreciation 12/31/2012 828us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenTwoZeroNwOneFiveAvenueMember
     
4740 NW 15th Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ft. Lauderdale, FL      
Initial Cost of Land 1,107us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourZeroNwOneFiveAvenueMember
     
Building and Improvements 3,111us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourZeroNwOneFiveAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 320us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourZeroNwOneFiveAvenueMember
     
Land 1,112us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourZeroNwOneFiveAvenueMember
     
Building and improvements 3,426us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourZeroNwOneFiveAvenueMember
     
Total 4,538us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourZeroNwOneFiveAvenueMember
     
Accumulated depreciation 12/31/2012 944us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFourZeroNwOneFiveAvenueMember
     
4750 NW 15th Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ft. Lauderdale, FL      
Initial Cost of Land 947us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFiveZeroNwOneFiveAvenueMember
     
Building and Improvements 3,079us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFiveZeroNwOneFiveAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 406us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFiveZeroNwOneFiveAvenueMember
     
Land 951us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFiveZeroNwOneFiveAvenueMember
     
Building and improvements 3,481us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFiveZeroNwOneFiveAvenueMember
     
Total 4,432us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFiveZeroNwOneFiveAvenueMember
     
Accumulated depreciation 12/31/2012 785us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenFiveZeroNwOneFiveAvenueMember
     
4800 NW 15th Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ft. Lauderdale, FL      
Initial Cost of Land 1,092us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightZeroZeroNwOneFiveAvenueMember
     
Building and Improvements 3,308us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightZeroZeroNwOneFiveAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 514us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightZeroZeroNwOneFiveAvenueMember
     
Land 1,097us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightZeroZeroNwOneFiveAvenueMember
     
Building and improvements 3,817us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightZeroZeroNwOneFiveAvenueMember
     
Total 4,914us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightZeroZeroNwOneFiveAvenueMember
     
Accumulated depreciation 12/31/2012 1,050us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourEightZeroZeroNwOneFiveAvenueMember
     
Medley Industrial Center [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Medley, FL      
Initial Cost of Land 857us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_MedleyIndustrialCenterMember
     
Building and Improvements 3,428us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_MedleyIndustrialCenterMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,988us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_MedleyIndustrialCenterMember
     
Land 864us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_MedleyIndustrialCenterMember
     
Building and improvements 7,409us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_MedleyIndustrialCenterMember
     
Total 8,273us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_MedleyIndustrialCenterMember
     
Accumulated depreciation 12/31/2012 1,687us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_MedleyIndustrialCenterMember
     
12601 &12605 NW 115th Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Medley, FL      
Initial Cost of Land 2,316us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroOneAndOneTwoSixZeroFiveNwOneOneSixAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 440us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroOneAndOneTwoSixZeroFiveNwOneOneSixAvenueMember
     
Land 762us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroOneAndOneTwoSixZeroFiveNwOneOneSixAvenueMember
     
Building and improvements 1,994us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroOneAndOneTwoSixZeroFiveNwOneOneSixAvenueMember
     
Total 2,756us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroOneAndOneTwoSixZeroFiveNwOneOneSixAvenueMember
     
Accumulated depreciation 12/31/2012 270us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroOneAndOneTwoSixZeroFiveNwOneOneSixAvenueMember
     
N25 W23255 Paul Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pewaukee, WI      
Initial Cost of Land 569us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NTwoFiveWTwoThreeTwoFiveFivePaulRoadMember
     
Building and Improvements 3,270us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NTwoFiveWTwoThreeTwoFiveFivePaulRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,836us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NTwoFiveWTwoThreeTwoFiveFivePaulRoadMember
     
Land 450us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NTwoFiveWTwoThreeTwoFiveFivePaulRoadMember
     
Building and improvements 5,225us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NTwoFiveWTwoThreeTwoFiveFivePaulRoadMember
     
Total 5,675us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NTwoFiveWTwoThreeTwoFiveFivePaulRoadMember
     
Accumulated depreciation 12/31/2012 1,880us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NTwoFiveWTwoThreeTwoFiveFivePaulRoadMember
     
5355 South Westridge Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) New Berlin, WI      
Encumbrances 5,089us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
Initial Cost of Land 1,630us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
Building and Improvements 7,058us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (108)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
Land 1,646us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
Building and improvements 6,934us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
Total 8,580us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
Accumulated depreciation 12/31/2012 1,643us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeFiveFiveSouthWestridgeDriveMember
     
320-334 W. Vogel Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Milwaukee, WI      
Encumbrances 2,692us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
Initial Cost of Land 506us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
Building and Improvements 3,199us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (100)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
Land 508us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
Building and improvements 3,097us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
Total 3,605us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
Accumulated depreciation 12/31/2012 1,481us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoZeroToThreeThreeFourWVogelAvenueMember
     
4950 South 6th Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Milwaukee, WI      
Encumbrances 1,444us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
Initial Cost of Land 299us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
Building and Improvements 1,565us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 273us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
Land 301us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
Building and improvements 1,836us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
Total 2,137us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
Accumulated depreciation 12/31/2012 1,026us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineFiveZeroSouthSixAvenueMember
     
17005 W. Ryerson Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) New Berlin, WI      
Encumbrances 2,915us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
Initial Cost of Land 403us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
Building and Improvements 3,647us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 251us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
Land 405us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
Building and improvements 3,896us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
Total 4,301us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
Accumulated depreciation 12/31/2012 1,549us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenZeroZeroFiveWRyersonRoadMember
     
W140 N9059 Lilly Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Menomonee Falls, WI      
Initial Cost of Land 343us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_WOneFourZeroNNineZeroFiveNineLillyRoadMember
     
Building and Improvements 1,153us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_WOneFourZeroNNineZeroFiveNineLillyRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 117us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_WOneFourZeroNNineZeroFiveNineLillyRoadMember
     
Land 366us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_WOneFourZeroNNineZeroFiveNineLillyRoadMember
     
Building and improvements 1,247us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_WOneFourZeroNNineZeroFiveNineLillyRoadMember
     
Total 1,613us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_WOneFourZeroNNineZeroFiveNineLillyRoadMember
     
Accumulated depreciation 12/31/2012 420us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_WOneFourZeroNNineZeroFiveNineLillyRoadMember
     
200 W. Vogel Avenue-Bldg B [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Milwaukee, WI      
Encumbrances 1,641us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
Initial Cost of Land 301us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
Building and Improvements 2,150us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (22)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
Land 302us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
Building and improvements 2,127us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
Total 2,429us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
Accumulated depreciation 12/31/2012 1,021us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroWVogelAvenueBuildingBMember
     
4921 S. 2nd Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Milwaukee, WI      
Initial Cost of Land 101us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineTwoOneSTwoStreetMember
     
Building and Improvements 713us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineTwoOneSTwoStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (196)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineTwoOneSTwoStreetMember
     
Land 58us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineTwoOneSTwoStreetMember
     
Building and improvements 560us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineTwoOneSTwoStreetMember
     
Total 618us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineTwoOneSTwoStreetMember
     
Accumulated depreciation 12/31/2012 278us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineTwoOneSTwoStreetMember
     
1500 Peebles Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Center, WI      
Initial Cost of Land 1,577us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroPeeblesDriveMember
     
Building and Improvements 1,018us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroPeeblesDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (278)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroPeeblesDriveMember
     
Land 1,528us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroPeeblesDriveMember
     
Building and improvements 789us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroPeeblesDriveMember
     
Total 2,317us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroPeeblesDriveMember
     
Accumulated depreciation 12/31/2012 697us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveZeroZeroPeeblesDriveMember
     
16600 West Glendale Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) New Berlin, WI      
Encumbrances 2,317us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
Initial Cost of Land 704us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
Building and Improvements 1,923us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 933us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
Land 715us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
Building and improvements 2,845us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
Total 3,560us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
Accumulated depreciation 12/31/2012 1,494us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixSixZeroZeroWestGlendaleAvenueMember
     
2485 Commerce Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) New Berlin, WI      
Encumbrances 1,386us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
Initial Cost of Land 483us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
Building and Improvements 1,516us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 131us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
Land 491us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
Building and improvements 1,639us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
Total 2,130us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
Accumulated depreciation 12/31/2012 743us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightFiveCommerceDriveMember
     
14518 Whittaker Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Menomonee Falls, WI      
Initial Cost of Land 437us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEightWhittakerWayMember
     
Building and Improvements 1,082us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEightWhittakerWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 382us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEightWhittakerWayMember
     
Land 445us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEightWhittakerWayMember
     
Building and improvements 1,456us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEightWhittakerWayMember
     
Total 1,901us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEightWhittakerWayMember
     
Accumulated depreciation 12/31/2012 538us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourFiveOneEightWhittakerWayMember
     
N58W15380 Shawn Circle [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Menomonee Falls, WI      
Initial Cost of Land 1,188us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NfiveEightWoneFiveThreeEightZeroShawnCircleMemberMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 16,931us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NfiveEightWoneFiveThreeEightZeroShawnCircleMemberMember
     
Land 1,204us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NfiveEightWoneFiveThreeEightZeroShawnCircleMemberMember
     
Building and improvements 16,915us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NfiveEightWoneFiveThreeEightZeroShawnCircleMemberMember
     
Total 18,119us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NfiveEightWoneFiveThreeEightZeroShawnCircleMemberMember
     
Accumulated depreciation 12/31/2012 3,014us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NfiveEightWoneFiveThreeEightZeroShawnCircleMemberMember
     
6201 West 111th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Bloomington, MN      
Encumbrances 3,293us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
Initial Cost of Land 1,358us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
Building and Improvements 8,622us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 13,466us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
Land 1,519us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
Building and improvements 21,927us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
Total 23,446us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
Accumulated depreciation 12/31/2012 11,065us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneWestOneOneOneThStreetMember
     
7251-7267 Washington Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Edina, MN      
Initial Cost of Land 129us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveOneAndSevenTwoSixSevenWashingtonAvenueMember
     
Building and Improvements 382us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveOneAndSevenTwoSixSevenWashingtonAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 871us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveOneAndSevenTwoSixSevenWashingtonAvenueMember
     
Land 182us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveOneAndSevenTwoSixSevenWashingtonAvenueMember
     
Building and improvements 1,200us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveOneAndSevenTwoSixSevenWashingtonAvenueMember
     
Total 1,382us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveOneAndSevenTwoSixSevenWashingtonAvenueMember
     
Accumulated depreciation 12/31/2012 842us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoFiveOneAndSevenTwoSixSevenWashingtonAvenueMember
     
7301-7325 Washington Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Edina, MN      
Initial Cost of Land 174us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeZeroOneAndSevenThreeTwoFiveWashingtonAvenueMember
     
Building and Improvements 391us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeZeroOneAndSevenThreeTwoFiveWashingtonAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 70us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeZeroOneAndSevenThreeTwoFiveWashingtonAvenueMember
     
Land 193us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeZeroOneAndSevenThreeTwoFiveWashingtonAvenueMember
     
Building and improvements 442us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeZeroOneAndSevenThreeTwoFiveWashingtonAvenueMember
     
Total 635us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeZeroOneAndSevenThreeTwoFiveWashingtonAvenueMember
     
Accumulated depreciation 12/31/2012 113us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThreeZeroOneAndSevenThreeTwoFiveWashingtonAvenueMember
     
7101 Winnetka Avenue North [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Brooklyn Park, MN      
Encumbrances 5,629us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
Initial Cost of Land 2,195us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
Building and Improvements 6,084us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,996us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
Land 2,228us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
Building and improvements 10,047us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
Total 12,275us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
Accumulated depreciation 12/31/2012 7,107us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroOneWinnetkaAvenueNorthMember
     
9901 West 74th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Encumbrances 3,303us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
Initial Cost of Land 621us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
Building and Improvements 3,289us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,291us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
Land 639us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
Building and improvements 6,562us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
Total 7,201us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
Accumulated depreciation 12/31/2012 5,599us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineNineZeroOneWestSevenFourThStreetMember
     
1030 Lone Oak Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eagan, MN      
Encumbrances 2,553us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
Initial Cost of Land 456us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
Building and Improvements 2,703us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 764us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
Land 456us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
Building and improvements 3,467us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
Total 3,923us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
Accumulated depreciation 12/31/2012 1,588us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeZeroLoneOakRoadMember
     
1060 Lone Oak Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eagan, MN      
Encumbrances 3,216us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
Initial Cost of Land 624us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
Building and Improvements 3,700us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 616us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
Land 624us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
Building and improvements 4,316us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
Total 4,940us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
Accumulated depreciation 12/31/2012 2,115us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixZeroLoneOakRoadMember
     
5400 Nathan Lane [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Plymouth, MN      
Encumbrances 2,826us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
Initial Cost of Land 749us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
Building and Improvements 4,461us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 951us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
Land 757us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
Building and improvements 5,404us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
Total 6,161us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
Accumulated depreciation 12/31/2012 2,660us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourZeroZeroNathanLaneMember
     
6655 Wedgewood Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Maple Grove, MN      
Initial Cost of Land 1,466us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveFiveWedgewoodRoadMember
     
Building and Improvements 8,342us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveFiveWedgewoodRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 4,267us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveFiveWedgewoodRoadMember
     
Land 1,466us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveFiveWedgewoodRoadMember
     
Building and improvements 12,609us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveFiveWedgewoodRoadMember
     
Total 14,075us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveFiveWedgewoodRoadMember
     
Accumulated depreciation 12/31/2012 5,446us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveFiveWedgewoodRoadMember
     
10120 W 76th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Initial Cost of Land 315us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneTwoZeroWSevenSixThStreetMember
     
Building and Improvements 1,804us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneTwoZeroWSevenSixThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,884us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneTwoZeroWSevenSixThStreetMember
     
Land 315us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneTwoZeroWSevenSixThStreetMember
     
Building and improvements 3,688us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneTwoZeroWSevenSixThStreetMember
     
Total 4,003us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneTwoZeroWSevenSixThStreetMember
     
Accumulated depreciation 12/31/2012 1,978us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneTwoZeroWSevenSixThStreetMember
     
12155 Nicollet Ave. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Burnsville, MN      
Initial Cost of Land 286us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoOneFiveFiveNicolletAveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,809us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoOneFiveFiveNicolletAveMember
     
Land 288us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoOneFiveFiveNicolletAveMember
     
Building and improvements 1,807us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoOneFiveFiveNicolletAveMember
     
Total 2,095us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoOneFiveFiveNicolletAveMember
     
Accumulated depreciation 12/31/2012 829us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoOneFiveFiveNicolletAveMember
     
4100 Peavey Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Chaska, MN      
Initial Cost of Land 277us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneZeroZeroPeaveyRoadMember
     
Building and Improvements 2,261us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneZeroZeroPeaveyRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 779us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneZeroZeroPeaveyRoadMember
     
Land 277us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneZeroZeroPeaveyRoadMember
     
Building and improvements 3,040us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneZeroZeroPeaveyRoadMember
     
Total 3,317us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneZeroZeroPeaveyRoadMember
     
Accumulated depreciation 12/31/2012 1,332us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneZeroZeroPeaveyRoadMember
     
5205 Highway 169 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Plymouth, MN      
Initial Cost of Land 446us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoZeroFiveHighwayOneSixNineMember
     
Building and Improvements 2,525us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoZeroFiveHighwayOneSixNineMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 891us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoZeroFiveHighwayOneSixNineMember
     
Land 578us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoZeroFiveHighwayOneSixNineMember
     
Building and improvements 3,284us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoZeroFiveHighwayOneSixNineMember
     
Total 3,862us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoZeroFiveHighwayOneSixNineMember
     
Accumulated depreciation 12/31/2012 1,526us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoZeroFiveHighwayOneSixNineMember
     
7100-7198 Shady Oak Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Encumbrances 4,569us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
Initial Cost of Land 715us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
Building and Improvements 4,054us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,252us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
Land 736us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
Building and improvements 6,285us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
Total 7,021us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
Accumulated depreciation 12/31/2012 2,484us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroZeroAndSevenOneNineEightShadyOakRoadMember
     
7500-7546 Washington Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Initial Cost of Land 229us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroZeroAndSevenFiveFourSixWashingtonSquareMember
     
Building and Improvements 1,300us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroZeroAndSevenFiveFourSixWashingtonSquareMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 881us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroZeroAndSevenFiveFourSixWashingtonSquareMember
     
Land 235us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroZeroAndSevenFiveFourSixWashingtonSquareMember
     
Building and improvements 2,175us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroZeroAndSevenFiveFourSixWashingtonSquareMember
     
Total 2,410us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroZeroAndSevenFiveFourSixWashingtonSquareMember
     
Accumulated depreciation 12/31/2012 928us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroZeroAndSevenFiveFourSixWashingtonSquareMember
     
7550-7586 Washington Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Initial Cost of Land 153us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveFiveZeroAndSevenFiveEightSixWashingtonSquareMember
     
Building and Improvements 867us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveFiveZeroAndSevenFiveEightSixWashingtonSquareMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 290us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveFiveZeroAndSevenFiveEightSixWashingtonSquareMember
     
Land 157us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveFiveZeroAndSevenFiveEightSixWashingtonSquareMember
     
Building and improvements 1,153us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveFiveZeroAndSevenFiveEightSixWashingtonSquareMember
     
Total 1,310us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveFiveZeroAndSevenFiveEightSixWashingtonSquareMember
     
Accumulated depreciation 12/31/2012 511us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveFiveZeroAndSevenFiveEightSixWashingtonSquareMember
     
5240-5300 Valley Industrial Blvd S [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shakopee, MN      
Encumbrances 2,450us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
Initial Cost of Land 362us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
Building and Improvements 2,049us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,215us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
Land 371us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
Building and improvements 3,255us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
Total 3,626us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
Accumulated depreciation 12/31/2012 1,215us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveTwoFourZeroAndFiveThreeZeroZeroValleyIndustrialBlvdSMember
     
500-530 Kasota Avenue SE [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Minneapolis, MN      
Initial Cost of Land 415us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroZeroAndFiveThreeZeroKasotaAvenueSeMember
     
Building and Improvements 2,354us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroZeroAndFiveThreeZeroKasotaAvenueSeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,276us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroZeroAndFiveThreeZeroKasotaAvenueSeMember
     
Land 434us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroZeroAndFiveThreeZeroKasotaAvenueSeMember
     
Building and improvements 3,611us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroZeroAndFiveThreeZeroKasotaAvenueSeMember
     
Total 4,045us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroZeroAndFiveThreeZeroKasotaAvenueSeMember
     
Accumulated depreciation 12/31/2012 1,467us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroZeroAndFiveThreeZeroKasotaAvenueSeMember
     
2530-2570 Kasota Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) St. Paul, MN      
Initial Cost of Land 407us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveThreeZeroAndTwoFiveSevenZeroKasotaAvenueMember
     
Building and Improvements 2,308us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveThreeZeroAndTwoFiveSevenZeroKasotaAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 964us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveThreeZeroAndTwoFiveSevenZeroKasotaAvenueMember
     
Land 441us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveThreeZeroAndTwoFiveSevenZeroKasotaAvenueMember
     
Building and improvements 3,238us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveThreeZeroAndTwoFiveSevenZeroKasotaAvenueMember
     
Total 3,679us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveThreeZeroAndTwoFiveSevenZeroKasotaAvenueMember
     
Accumulated depreciation 12/31/2012 1,315us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveThreeZeroAndTwoFiveSevenZeroKasotaAvenueMember
     
5775 12th Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shakopee, MN      
Encumbrances 3,965us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenSevenFiveOneTwoThAvenueMember
     
Initial Cost of Land 590us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenSevenFiveOneTwoThAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 5,279us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenSevenFiveOneTwoThAvenueMember
     
Land 590us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenSevenFiveOneTwoThAvenueMember
     
Building and improvements 5,279us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenSevenFiveOneTwoThAvenueMember
     
Total 5,869us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenSevenFiveOneTwoThAvenueMember
     
Accumulated depreciation 12/31/2012 2,103us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenSevenFiveOneTwoThAvenueMember
     
1157 Valley Park Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shakopee, MN      
Encumbrances 3,969us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveSevenValleyParkDriveMember
     
Initial Cost of Land 760us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveSevenValleyParkDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 6,803us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveSevenValleyParkDriveMember
     
Land 888us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveSevenValleyParkDriveMember
     
Building and improvements 6,675us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveSevenValleyParkDriveMember
     
Total 7,563us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveSevenValleyParkDriveMember
     
Accumulated depreciation 12/31/2012 2,579us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveSevenValleyParkDriveMember
     
9600 West 76th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Encumbrances 2,325us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
Initial Cost of Land 1,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
Building and Improvements 2,450us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 483us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
Land 1,034us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
Building and improvements 2,899us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
Total 3,933us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
Accumulated depreciation 12/31/2012 968us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroZeroWestSevenSixThStreetMember
     
9700 West 76th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Encumbrances 3,151us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
Initial Cost of Land 1,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
Building and Improvements 2,709us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,007us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
Land 1,038us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
Building and improvements 3,678us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
Total 4,716us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
Accumulated depreciation 12/31/2012 1,284us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSevenZeroZeroWestSevenSixThStreetMember
     
7600 69th Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Greenfield, MN      
Initial Cost of Land 1,500us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenSixZeroZeroSixNineThAvenueMember
     
Building and Improvements 8,328us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenSixZeroZeroSixNineThAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,391us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenSixZeroZeroSixNineThAvenueMember
     
Land 1,510us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenSixZeroZeroSixNineThAvenueMember
     
Building and improvements 9,709us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenSixZeroZeroSixNineThAvenueMember
     
Total 11,219us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenSixZeroZeroSixNineThAvenueMember
     
Accumulated depreciation 12/31/2012 3,571us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenSixZeroZeroSixNineThAvenueMember
     
5017 Boone Avenue North [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) New Hope, MN      
Initial Cost of Land 1,000us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroOneSevenBooneAvenueNorthMember
     
Building and Improvements 1,599us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroOneSevenBooneAvenueNorthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (6)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroOneSevenBooneAvenueNorthMember
     
Land 1,009us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroOneSevenBooneAvenueNorthMember
     
Building and improvements 1,584us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroOneSevenBooneAvenueNorthMember
     
Total 2,593us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroOneSevenBooneAvenueNorthMember
     
Accumulated depreciation 12/31/2012 813us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroOneSevenBooneAvenueNorthMember
     
2300 West Highway 13 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Burnsville, MN      
Initial Cost of Land 2,517us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroWestHighwayOneThreeMember
     
Building and Improvements 6,069us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroWestHighwayOneThreeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,651)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroWestHighwayOneThreeMember
     
Land 1,296us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroWestHighwayOneThreeMember
     
Building and improvements 5,639us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroWestHighwayOneThreeMember
     
Total 6,935us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroWestHighwayOneThreeMember
     
Accumulated depreciation 12/31/2012 3,449us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroWestHighwayOneThreeMember
     
1087 Park Place [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shakopee, MN      
Encumbrances 4,218us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
Initial Cost of Land 1,195us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
Building and Improvements 4,891us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (409)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
Land 1,198us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
Building and improvements 4,479us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
Total 5,677us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
Accumulated depreciation 12/31/2012 1,091us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroEightSevenParkPlaceMember
     
5391 12th Avenue SE [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shakopee, MN      
Encumbrances 4,381us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
Initial Cost of Land 1,392us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
Building and Improvements 8,149us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (495)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
Land 1,395us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
Building and improvements 7,651us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
Total 9,046us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
Accumulated depreciation 12/31/2012 1,915us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeNineOneOneTwoThAvenueSeMember
     
4701 Valley Industrial Blvd S [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Shakopee, MN      
Encumbrances 5,483us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
Initial Cost of Land 1,296us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
Building and Improvements 7,157us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (337)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
Land 1,299us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
Building and improvements 6,817us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
Total 8,116us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
Accumulated depreciation 12/31/2012 2,477us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneValleyIndustrialBlvdSMember
     
6455 City West Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eden Prairie, MN      
Initial Cost of Land 659us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveFiveCityWestParkwayMember
     
Building and Improvements 3,189us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveFiveCityWestParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 949us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveFiveCityWestParkwayMember
     
Land 665us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveFiveCityWestParkwayMember
     
Building and improvements 4,132us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveFiveCityWestParkwayMember
     
Total 4,797us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveFiveCityWestParkwayMember
     
Accumulated depreciation 12/31/2012 974us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveFiveCityWestParkwayMember
     
7035 Winnetka Avene North [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Brooklyn Park, MN      
Encumbrances 4,076us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroThreeFiveWinnetkaAvenueNorthMember
     
Initial Cost of Land 1,275us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroThreeFiveWinnetkaAvenueNorthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 6,492us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroThreeFiveWinnetkaAvenueNorthMember
     
Land 1,343us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroThreeFiveWinnetkaAvenueNorthMember
     
Building and improvements 6,424us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroThreeFiveWinnetkaAvenueNorthMember
     
Total 7,767us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroThreeFiveWinnetkaAvenueNorthMember
     
Accumulated depreciation 12/31/2012 1,245us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenZeroThreeFiveWinnetkaAvenueNorthMember
     
139 Eva Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) St. Paul, MN      
Initial Cost of Land 2,132us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeNineEvaStreetMember
     
Building and Improvements 3,105us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeNineEvaStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (286)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeNineEvaStreetMember
     
Land 2,175us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeNineEvaStreetMember
     
Building and improvements 2,776us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeNineEvaStreetMember
     
Total 4,951us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeNineEvaStreetMember
     
Accumulated depreciation 12/31/2012 560us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeNineEvaStreetMember
     
21900 Dodd Boulevard [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Lakeville, MN      
Encumbrances 9,031us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Initial Cost of Land 2,289us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Building and Improvements 7,952us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 0us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Land 2,289us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Building and improvements 7,952us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Total 10,241us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Accumulated depreciation 12/31/2012 1,692us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneNineZeroZeroDoddBoulevardMember
     
Three Hundred Seventy Five Rivertown Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Woodbury, MN      
Encumbrances 7,058us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Initial Cost of Land 2,635us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Building and Improvements 8,157us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 48us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Land 2,635us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Building and improvements 8,205us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Total 10,840us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Accumulated depreciation 12/31/2012 407us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeHundredSeventyFiveRivertownDriveMember
     
Nine Hundred Thirty Five Aldrin Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Eagan, MN      
Initial Cost of Land 2,096us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredThirtyFiveAldrinDriveMember
     
Building and Improvements 7,884us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredThirtyFiveAldrinDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredThirtyFiveAldrinDriveMember
     
Land 2,096us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredThirtyFiveAldrinDriveMember
     
Building and improvements 7,885us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredThirtyFiveAldrinDriveMember
     
Total 9,981us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredThirtyFiveAldrinDriveMember
     
Accumulated depreciation 12/31/2012 65us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineHundredThirtyFiveAldrinDriveMember
     
Seven Thousand Fifty Winnetka Avenue North [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Brooklyn Park, MN      
Initial Cost of Land 1,623us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyWinnetkaAvenueNorthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 7,792us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyWinnetkaAvenueNorthMember
     
Land 1,632us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyWinnetkaAvenueNorthMember
     
Building and improvements 7,783us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyWinnetkaAvenueNorthMember
     
Total 9,415us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyWinnetkaAvenueNorthMember
     
Seven Thousand Fifty One West Broadway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Brooklyn Park, MN      
Initial Cost of Land 1,275us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyOneWestBroadwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 5,246us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyOneWestBroadwayMember
     
Land 1,277us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyOneWestBroadwayMember
     
Building and improvements 5,244us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyOneWestBroadwayMember
     
Total 6,521us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenThousandFiftyOneWestBroadwayMember
     
1621 Heil Quaker Boulevard [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Nashville, TN      
Encumbrances 1,945us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
Initial Cost of Land 413us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
Building and Improvements 2,383us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 984us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
Land 430us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
Building and improvements 3,350us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
Total 3,780us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
Accumulated depreciation 12/31/2012 1,594us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoOneHeilQuakerBoulevardMember
     
3099 Barry Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Portland, TN      
Initial Cost of Land 418us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineNineBarryDriveMember
     
Building and Improvements 2,368us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineNineBarryDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (683)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineNineBarryDriveMember
     
Land 248us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineNineBarryDriveMember
     
Building and improvements 1,855us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineNineBarryDriveMember
     
Total 2,103us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineNineBarryDriveMember
     
Accumulated depreciation 12/31/2012 1,022us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineNineBarryDriveMember
     
1931 Air Lane Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Nashville, TN      
Encumbrances 2,344us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
Initial Cost of Land 489us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
Building and Improvements 2,785us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 327us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
Land 493us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
Building and improvements 3,108us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
Total 3,601us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
Accumulated depreciation 12/31/2012 1,326us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineThreeOneAirLaneDriveMember
     
4640 Cummings Park [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Nashville, TN      
Encumbrances 2,053us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
Initial Cost of Land 360us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
Building and Improvements 2,040us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 638us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
Land 365us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
Building and improvements 2,673us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
Total 3,038us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
Accumulated depreciation 12/31/2012 957us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSixFourZeroCummingsParkMember
     
1740 River Hills Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Nashville, TN      
Encumbrances 2,759us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
Initial Cost of Land 848us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
Building and Improvements 4,383us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 607us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
Land 888us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
Building and improvements 4,950us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
Total 5,838us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
Accumulated depreciation 12/31/2012 1,933us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSevenFourZeroRiverHillsDriveMember
     
211 Ellery Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Nashville, TN      
Encumbrances 2,727us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
Initial Cost of Land 606us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
Building and Improvements 3,192us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 349us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
Land 616us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
Building and improvements 3,531us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
Total 4,147us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
Accumulated depreciation 12/31/2012 1,098us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneOneElleryCourtMember
     
130 Maddox Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Gallatin, TN      
Encumbrances 15,636us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroMaddoxRoadMember
     
Initial Cost of Land 1,778us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroMaddoxRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 23,548us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroMaddoxRoadMember
     
Land 1,778us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroMaddoxRoadMember
     
Building and improvements 23,548us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroMaddoxRoadMember
     
Total 25,326us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroMaddoxRoadMember
     
Accumulated depreciation 12/31/2012 3,490us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeZeroMaddoxRoadMember
     
14 World's Fair Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Franklin, NJ      
Initial Cost of Land 483us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourWorldsFairDriveMember
     
Building and Improvements 2,735us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourWorldsFairDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 717us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourWorldsFairDriveMember
     
Land 503us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourWorldsFairDriveMember
     
Building and improvements 3,432us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourWorldsFairDriveMember
     
Total 3,935us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourWorldsFairDriveMember
     
Accumulated depreciation 12/31/2012 1,490us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourWorldsFairDriveMember
     
12 World's Fair Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Franklin, NJ      
Initial Cost of Land 572us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoWorldsFairDriveMember
     
Building and Improvements 3,240us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoWorldsFairDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,071us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoWorldsFairDriveMember
     
Land 593us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoWorldsFairDriveMember
     
Building and improvements 4,290us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoWorldsFairDriveMember
     
Total 4,883us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoWorldsFairDriveMember
     
Accumulated depreciation 12/31/2012 1,887us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoWorldsFairDriveMember
     
22 World's Fair Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Franklin, NJ      
Initial Cost of Land 364us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoWorldsFairDriveMember
     
Building and Improvements 2,064us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoWorldsFairDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 533us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoWorldsFairDriveMember
     
Land 375us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoWorldsFairDriveMember
     
Building and improvements 2,586us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoWorldsFairDriveMember
     
Total 2,961us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoWorldsFairDriveMember
     
Accumulated depreciation 12/31/2012 1,029us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoWorldsFairDriveMember
     
26 World's Fair Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Franklin, NJ      
Initial Cost of Land 361us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixWorldsFairDriveMember
     
Building and Improvements 2,048us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixWorldsFairDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 523us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixWorldsFairDriveMember
     
Land 377us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixWorldsFairDriveMember
     
Building and improvements 2,555us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixWorldsFairDriveMember
     
Total 2,932us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixWorldsFairDriveMember
     
Accumulated depreciation 12/31/2012 1,052us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixWorldsFairDriveMember
     
24 World's Fair Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Franklin, NJ      
Initial Cost of Land 347us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourWorldsFairDriveMember
     
Building and Improvements 1,968us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourWorldsFairDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 490us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourWorldsFairDriveMember
     
Land 362us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourWorldsFairDriveMember
     
Building and improvements 2,443us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourWorldsFairDriveMember
     
Total 2,805us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourWorldsFairDriveMember
     
Accumulated depreciation 12/31/2012 1,040us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourWorldsFairDriveMember
     
20 World's Fair Drive Lot 13 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Sumerset, NJ      
Initial Cost of Land 9us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroWorldsFairDriveLotOneThreeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,576us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroWorldsFairDriveLotOneThreeMember
     
Land 691us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroWorldsFairDriveLotOneThreeMember
     
Building and improvements 1,894us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroWorldsFairDriveLotOneThreeMember
     
Total 2,585us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroWorldsFairDriveLotOneThreeMember
     
Accumulated depreciation 12/31/2012 657us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroWorldsFairDriveLotOneThreeMember
     
45 Route 46 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 969us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveRouteFourSixMember
     
Building and Improvements 5,491us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveRouteFourSixMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 913us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveRouteFourSixMember
     
Land 978us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveRouteFourSixMember
     
Building and improvements 6,395us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveRouteFourSixMember
     
Total 7,373us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveRouteFourSixMember
     
Accumulated depreciation 12/31/2012 2,256us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveRouteFourSixMember
     
43 Route 46 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 474us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeRouteFourSixMember
     
Building and Improvements 2,686us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeRouteFourSixMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 551us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeRouteFourSixMember
     
Land 479us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeRouteFourSixMember
     
Building and improvements 3,232us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeRouteFourSixMember
     
Total 3,711us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeRouteFourSixMember
     
Accumulated depreciation 12/31/2012 1,223us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeRouteFourSixMember
     
39 Route 46 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 260us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineRouteFourSixMember
     
Building and Improvements 1,471us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineRouteFourSixMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 197us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineRouteFourSixMember
     
Land 262us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineRouteFourSixMember
     
Building and improvements 1,666us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineRouteFourSixMember
     
Total 1,928us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineRouteFourSixMember
     
Accumulated depreciation 12/31/2012 583us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeNineRouteFourSixMember
     
26 Chapin Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 956us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixChapinRoadMember
     
Building and Improvements 5,415us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixChapinRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 672us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixChapinRoadMember
     
Land 965us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixChapinRoadMember
     
Building and improvements 6,078us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixChapinRoadMember
     
Total 7,043us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixChapinRoadMember
     
Accumulated depreciation 12/31/2012 2,177us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixChapinRoadMember
     
30 Chapin Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 960us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroChapinRoadMember
     
Building and Improvements 5,440us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroChapinRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 499us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroChapinRoadMember
     
Land 969us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroChapinRoadMember
     
Building and improvements 5,930us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroChapinRoadMember
     
Total 6,899us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroChapinRoadMember
     
Accumulated depreciation 12/31/2012 2,080us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroChapinRoadMember
     
20 Hook Mountain Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 1,507us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroHookMountainRoadMember
     
Building and Improvements 8,542us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroHookMountainRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,809us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroHookMountainRoadMember
     
Land 1,534us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroHookMountainRoadMember
     
Building and improvements 11,324us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroHookMountainRoadMember
     
Total 12,858us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroHookMountainRoadMember
     
Accumulated depreciation 12/31/2012 4,700us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroHookMountainRoadMember
     
30 Hook Mountain Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 389us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroHookMountainRoadMember
     
Building and Improvements 2,206us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroHookMountainRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 539us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroHookMountainRoadMember
     
Land 396us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroHookMountainRoadMember
     
Building and improvements 2,738us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroHookMountainRoadMember
     
Total 3,134us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroHookMountainRoadMember
     
Accumulated depreciation 12/31/2012 977us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroHookMountainRoadMember
     
16 Chapin Rod [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 885us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixChapinRodMember
     
Building and Improvements 5,015us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixChapinRodMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 516us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixChapinRodMember
     
Land 901us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixChapinRodMember
     
Building and improvements 5,515us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixChapinRodMember
     
Total 6,416us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixChapinRodMember
     
Accumulated depreciation 12/31/2012 1,924us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixChapinRodMember
     
20 Chapin Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pine Brook, NJ      
Initial Cost of Land 1,134us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroChapinRoadMember
     
Building and Improvements 6,426us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroChapinRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 598us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroChapinRoadMember
     
Land 1,154us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroChapinRoadMember
     
Building and improvements 7,004us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroChapinRoadMember
     
Total 8,158us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroChapinRoadMember
     
Accumulated depreciation 12/31/2012 2,383us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroChapinRoadMember
     
2500 Main Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Sayreville, NJ      
Initial Cost of Land 944us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroMainStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 4,558us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroMainStreetMember
     
Land 944us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroMainStreetMember
     
Building and improvements 4,558us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroMainStreetMember
     
Total 5,502us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroMainStreetMember
     
Accumulated depreciation 12/31/2012 1,319us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveZeroZeroMainStreetMember
     
2400 Main Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Sayreville, NJ      
Initial Cost of Land 996us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroZeroMainStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 5,575us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroZeroMainStreetMember
     
Land 996us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroZeroMainStreetMember
     
Building and improvements 5,575us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroZeroMainStreetMember
     
Total 6,571us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroZeroMainStreetMember
     
Accumulated depreciation 12/31/2012 1,507us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourZeroZeroMainStreetMember
     
309-319 Pierce Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Somerset, NJ      
Encumbrances 3,283us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
Initial Cost of Land 1,300us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
Building and Improvements 4,628us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,020us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
Land 1,309us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
Building and improvements 5,639us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
Total 6,948us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
Accumulated depreciation 12/31/2012 1,968us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroNineAndThreeOneThreePierceStreetMember
     
230-240 Welsh Pool Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Exton, PA      
Initial Cost of Land 154us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroAndTwoFourZeroWelshPoolRoadMember
     
Building and Improvements 851us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroAndTwoFourZeroWelshPoolRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 355us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroAndTwoFourZeroWelshPoolRoadMember
     
Land 170us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroAndTwoFourZeroWelshPoolRoadMember
     
Building and improvements 1,190us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroAndTwoFourZeroWelshPoolRoadMember
     
Total 1,360us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroAndTwoFourZeroWelshPoolRoadMember
     
Accumulated depreciation 12/31/2012 438us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroAndTwoFourZeroWelshPoolRoadMember
     
254 Welsh Pool Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Exton, PA      
Initial Cost of Land 75us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveFourWelshPoolRoadMember
     
Building and Improvements 418us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveFourWelshPoolRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 206us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveFourWelshPoolRoadMember
     
Land 91us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveFourWelshPoolRoadMember
     
Building and improvements 608us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveFourWelshPoolRoadMember
     
Total 699us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveFourWelshPoolRoadMember
     
Accumulated depreciation 12/31/2012 255us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFiveFourWelshPoolRoadMember
     
243-251 Welsh Pool Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Exton, PA      
Initial Cost of Land 144us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourThreeToTwoFiveOneWelshPoolRoadMember
     
Building and Improvements 796us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourThreeToTwoFiveOneWelshPoolRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 441us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourThreeToTwoFiveOneWelshPoolRoadMember
     
Land 159us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourThreeToTwoFiveOneWelshPoolRoadMember
     
Building and improvements 1,222us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourThreeToTwoFiveOneWelshPoolRoadMember
     
Total 1,381us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourThreeToTwoFiveOneWelshPoolRoadMember
     
Accumulated depreciation 12/31/2012 446us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourThreeToTwoFiveOneWelshPoolRoadMember
     
151-161 Philips Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Exton, PA      
Initial Cost of Land 191us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveOneAndOneSixOnePhilipsRoadMember
     
Building and Improvements 1,059us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveOneAndOneSixOnePhilipsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 345us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveOneAndOneSixOnePhilipsRoadMember
     
Land 229us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveOneAndOneSixOnePhilipsRoadMember
     
Building and improvements 1,366us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveOneAndOneSixOnePhilipsRoadMember
     
Total 1,595us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveOneAndOneSixOnePhilipsRoadMember
     
Accumulated depreciation 12/31/2012 553us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveOneAndOneSixOnePhilipsRoadMember
     
216 Philips Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Exton, PA      
Initial Cost of Land 199us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSixPhilipsRoadMember
     
Building and Improvements 1,100us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSixPhilipsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 498us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSixPhilipsRoadMember
     
Land 220us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSixPhilipsRoadMember
     
Building and improvements 1,577us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSixPhilipsRoadMember
     
Total 1,797us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSixPhilipsRoadMember
     
Accumulated depreciation 12/31/2012 689us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSixPhilipsRoadMember
     
14 McFadden Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Palmer, PA      
Initial Cost of Land 600us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourMcfaddenRoadMember
     
Building and Improvements 1,349us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourMcfaddenRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (274)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourMcfaddenRoadMember
     
Land 625us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourMcfaddenRoadMember
     
Building and improvements 1,050us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourMcfaddenRoadMember
     
Total 1,675us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourMcfaddenRoadMember
     
Accumulated depreciation 12/31/2012 265us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourMcfaddenRoadMember
     
2801 Red Lion Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Philadelphia, PA      
Initial Cost of Land 950us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightZeroOneRedLionRoadMember
     
Building and Improvements 5,916us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightZeroOneRedLionRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (51)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightZeroOneRedLionRoadMember
     
Land 964us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightZeroOneRedLionRoadMember
     
Building and improvements 5,851us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightZeroOneRedLionRoadMember
     
Total 6,815us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightZeroOneRedLionRoadMember
     
Accumulated depreciation 12/31/2012 2,214us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightZeroOneRedLionRoadMember
     
3240 S. 78th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Philadelphia, PA      
Initial Cost of Land 515us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourZeroSSevenEightThStreetMember
     
Building and Improvements 1,245us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourZeroSSevenEightThStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (492)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourZeroSSevenEightThStreetMember
     
Land 423us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourZeroSSevenEightThStreetMember
     
Building and improvements 845us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourZeroSSevenEightThStreetMember
     
Total 1,268us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourZeroSSevenEightThStreetMember
     
Accumulated depreciation 12/31/2012 251us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeTwoFourZeroSSevenEightThStreetMember
     
200 Cascade Drive, Bldg. 1 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Allentown, PA      
Encumbrances 16,944us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
Initial Cost of Land 2,133us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
Building and Improvements 17,562us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 366us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
Land 2,769us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
Building and improvements 17,292us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
Total 20,061us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
Accumulated depreciation 12/31/2012 4,972us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgOneMember
     
200 Cascade Drive, Bldg. 2 [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Allentown, PA      
Encumbrances 2,334us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
Initial Cost of Land 310us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
Building and Improvements 2,268us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 174us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
Land 316us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
Building and improvements 2,436us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
Total 2,752us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
Accumulated depreciation 12/31/2012 690us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroCascadeDriveBldgTwoMember
     
6300 Bristol Pike [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Levittown, PA      
Initial Cost of Land 1,074us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroZeroBristolPikeMember
     
Building and Improvements 2,642us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroZeroBristolPikeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (194)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroZeroBristolPikeMember
     
Land 964us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroZeroBristolPikeMember
     
Building and improvements 2,558us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroZeroBristolPikeMember
     
Total 3,522us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroZeroBristolPikeMember
     
Accumulated depreciation 12/31/2012 1,523us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroZeroBristolPikeMember
     
2455 Boulevard of Generals [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Norristown, PA      
Encumbrances 3,235us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
Initial Cost of Land 1,200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
Building and Improvements 4,800us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 846us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
Land 1,226us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
Building and improvements 5,620us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
Total 6,846us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
Accumulated depreciation 12/31/2012 1,894us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveFiveBoulevardOfGeneralsMember
     
1045 South Edward Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tempe, AZ      
Initial Cost of Land 390us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourFiveSouthEdwardDriveMember
     
Building and Improvements 2,160us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourFiveSouthEdwardDriveMember
     
Land 396us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourFiveSouthEdwardDriveMember
     
Building and improvements 2,524us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourFiveSouthEdwardDriveMember
     
Total 2,920us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourFiveSouthEdwardDriveMember
     
Accumulated depreciation 12/31/2012 877us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourFiveSouthEdwardDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 370us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourFiveSouthEdwardDriveMember
     
50 South 56th Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Chandler, AZ      
Encumbrances 3,766us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
Initial Cost of Land 1,206us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
Building and Improvements 3,218us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
Land 1,252us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
Building and improvements 4,534us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
Total 5,786us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
Accumulated depreciation 12/31/2012 1,224us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,362us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroSouthFiveSixStreetMember
     
4701 W. Jefferson [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Phoenix, AZ      
Encumbrances 2,508us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
Initial Cost of Land 926us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
Building and Improvements 2,195us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
Land 929us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
Building and improvements 2,635us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
Total 3,564us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
Accumulated depreciation 12/31/2012 1,418us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 443us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourSevenZeroOneWJeffersonMember
     
7102 W. Roosevelt [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Phoenix, AZ      
Initial Cost of Land 1,613us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroTwoWRooseveltMember
     
Building and Improvements 6,451us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroTwoWRooseveltMember
     
Land 1,620us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroTwoWRooseveltMember
     
Building and improvements 6,788us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroTwoWRooseveltMember
     
Total 8,408us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroTwoWRooseveltMember
     
Accumulated depreciation 12/31/2012 2,207us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroTwoWRooseveltMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 344us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenOneZeroTwoWRooseveltMember
     
4137 West Adams Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Phoenix, AZ      
Initial Cost of Land 990us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneThreeSevenWestAdamsStreetMember
     
Building and Improvements 2,661us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneThreeSevenWestAdamsStreetMember
     
Land 1,038us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneThreeSevenWestAdamsStreetMember
     
Building and improvements 3,080us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneThreeSevenWestAdamsStreetMember
     
Total 4,118us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneThreeSevenWestAdamsStreetMember
     
Accumulated depreciation 12/31/2012 1,039us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneThreeSevenWestAdamsStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 467us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourOneThreeSevenWestAdamsStreetMember
     
245 W. Lodge [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tempe, AZ      
Initial Cost of Land 898us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveWLodgeMember
     
Building and Improvements 3,066us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveWLodgeMember
     
Land 362us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveWLodgeMember
     
Building and improvements 1,712us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveWLodgeMember
     
Total 2,074us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveWLodgeMember
     
Accumulated depreciation 12/31/2012 710us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveWLodgeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,890)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourFiveWLodgeMember
     
1590 E Riverview Dr. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Phoenix, AZ      
Encumbrances 4,721us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
Initial Cost of Land 1,293us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
Building and Improvements 5,950us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
Land 1,292us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
Building and improvements 6,354us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
Total 7,646us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
Accumulated depreciation 12/31/2012 1,396us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 403us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFiveNineZeroERiverviewDrMember
     
14131 N. Rio Vista Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Peoria, AZ      
Initial Cost of Land 2,563us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourOneThreeOneNRioVistaDrMember
     
Building and Improvements 9,388us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourOneThreeOneNRioVistaDrMember
     
Land 2,563us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourOneThreeOneNRioVistaDrMember
     
Building and improvements 10,489us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourOneThreeOneNRioVistaDrMember
     
Total 13,052us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourOneThreeOneNRioVistaDrMember
     
Accumulated depreciation 12/31/2012 2,665us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourOneThreeOneNRioVistaDrMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,101us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourOneThreeOneNRioVistaDrMember
     
8716 W. Ludlow Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Peoria, AZ      
Initial Cost of Land 2,709us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenOneSixWLudlowDriveMember
     
Building and Improvements 10,970us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenOneSixWLudlowDriveMember
     
Land 2,709us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenOneSixWLudlowDriveMember
     
Building and improvements 12,363us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenOneSixWLudlowDriveMember
     
Total 15,072us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenOneSixWLudlowDriveMember
     
Accumulated depreciation 12/31/2012 2,869us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenOneSixWLudlowDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,393us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightSevenOneSixWLudlowDriveMember
     
3815 W. Washington St. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Phoenix, AZ      
Encumbrances 3,589us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
Initial Cost of Land 1,675us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
Building and Improvements 4,514us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
Land 1,719us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
Building and improvements 4,619us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
Total 6,338us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
Accumulated depreciation 12/31/2012 959us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 149us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeEightOneFiveWWashingtonStreetMember
     
9180 W. Buckeye Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tolleson, AZ      
Encumbrances 7,021us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Initial Cost of Land 1,904us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Building and Improvements 6,805us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Land 1,923us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Building and improvements 9,354us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Total 11,277us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Accumulated depreciation 12/31/2012 1,665us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,568us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionCarryingCosts
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineOneEightZeroWbuckeyeRoadMember
     
Eight Thousand Six Hundred Forty Four West Ludlow Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Peoria, AZ      
Initial Cost of Land 1,726us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredFortyFourWestLudlowDriveMember
     
Building and Improvements 7,216us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredFortyFourWestLudlowDriveMember
     
Land 1,726us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredFortyFourWestLudlowDriveMember
     
Building and improvements 7,216us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredFortyFourWestLudlowDriveMember
     
Total 8,942us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredFortyFourWestLudlowDriveMember
     
Accumulated depreciation 12/31/2012 43us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredFortyFourWestLudlowDriveMember
     
Eight Thousand Six Hundred Six West Ludlow Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Peoria, AZ      
Initial Cost of Land 956us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSixWestLudlowDriveMember
     
Building and Improvements 2,668us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSixWestLudlowDriveMember
     
Land 956us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSixWestLudlowDriveMember
     
Building and improvements 2,668us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSixWestLudlowDriveMember
     
Total 3,624us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSixWestLudlowDriveMember
     
Accumulated depreciation 12/31/2012 17us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSixWestLudlowDriveMember
     
Eight Thousand Six Hundred Seventy Nine West Ludlow Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Peoria, AZ      
Initial Cost of Land 672us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSeventyNineWestLudlowDriveMember
     
Building and Improvements 2,791us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSeventyNineWestLudlowDriveMember
     
Land 672us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSeventyNineWestLudlowDriveMember
     
Building and improvements 2,791us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSeventyNineWestLudlowDriveMember
     
Total 3,463us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSeventyNineWestLudlowDriveMember
     
Accumulated depreciation 12/31/2012 17us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightThousandSixHundredSeventyNineWestLudlowDriveMember
     
1270 West 2320 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 138us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroWestTwoThreeTwoZeroSouthMember
     
Building and Improvements 784us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroWestTwoThreeTwoZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 144us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroWestTwoThreeTwoZeroSouthMember
     
Land 143us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroWestTwoThreeTwoZeroSouthMember
     
Building and improvements 923us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroWestTwoThreeTwoZeroSouthMember
     
Total 1,066us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroWestTwoThreeTwoZeroSouthMember
     
Accumulated depreciation 12/31/2012 362us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroWestTwoThreeTwoZeroSouthMember
     
1275 West 2240 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 395us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenFiveWestTwoTwoFourZeroSouthMember
     
Building and Improvements 2,241us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenFiveWestTwoTwoFourZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 352us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenFiveWestTwoTwoFourZeroSouthMember
     
Land 408us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenFiveWestTwoTwoFourZeroSouthMember
     
Building and improvements 2,580us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenFiveWestTwoTwoFourZeroSouthMember
     
Total 2,988us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenFiveWestTwoTwoFourZeroSouthMember
     
Accumulated depreciation 12/31/2012 1,032us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenFiveWestTwoTwoFourZeroSouthMember
     
1288 West 2240 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 119us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightWestTwoTwoFourZeroSouthMember
     
Building and Improvements 672us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightWestTwoTwoFourZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 136us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightWestTwoTwoFourZeroSouthMember
     
Land 123us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightWestTwoTwoFourZeroSouthMember
     
Building and improvements 804us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightWestTwoTwoFourZeroSouthMember
     
Total 927us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightWestTwoTwoFourZeroSouthMember
     
Accumulated depreciation 12/31/2012 319us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightEightWestTwoTwoFourZeroSouthMember
     
2235 South 1300 West [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 198us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoThreeFiveSouthOneThreeZeroZeroWestMember
     
Building and Improvements 1,120us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoThreeFiveSouthOneThreeZeroZeroWestMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 168us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoThreeFiveSouthOneThreeZeroZeroWestMember
     
Land 204us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoThreeFiveSouthOneThreeZeroZeroWestMember
     
Building and improvements 1,282us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoThreeFiveSouthOneThreeZeroZeroWestMember
     
Total 1,486us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoThreeFiveSouthOneThreeZeroZeroWestMember
     
Accumulated depreciation 12/31/2012 512us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoThreeFiveSouthOneThreeZeroZeroWestMember
     
1293 West 2200 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 158us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineThreeWestTwoTwoZeroZeroSouthMember
     
Building and Improvements 896us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineThreeWestTwoTwoZeroZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 282us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineThreeWestTwoTwoZeroZeroSouthMember
     
Land 163us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineThreeWestTwoTwoZeroZeroSouthMember
     
Building and improvements 1,173us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineThreeWestTwoTwoZeroZeroSouthMember
     
Total 1,336us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineThreeWestTwoTwoZeroZeroSouthMember
     
Accumulated depreciation 12/31/2012 471us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineThreeWestTwoTwoZeroZeroSouthMember
     
1279 West 2200 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 198us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenNineWestTwoTwoZeroZeroSouthMember
     
Building and Improvements 1,120us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenNineWestTwoTwoZeroZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 369us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenNineWestTwoTwoZeroZeroSouthMember
     
Land 204us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenNineWestTwoTwoZeroZeroSouthMember
     
Building and improvements 1,483us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenNineWestTwoTwoZeroZeroSouthMember
     
Total 1,687us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenNineWestTwoTwoZeroZeroSouthMember
     
Accumulated depreciation 12/31/2012 715us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenNineWestTwoTwoZeroZeroSouthMember
     
1272 West 2240 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 336us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenTwoWestTwoTwoFourZeroSouthMember
     
Building and Improvements 1,905us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenTwoWestTwoTwoFourZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 410us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenTwoWestTwoTwoFourZeroSouthMember
     
Land 347us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenTwoWestTwoTwoFourZeroSouthMember
     
Building and improvements 2,304us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenTwoWestTwoTwoFourZeroSouthMember
     
Total 2,651us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenTwoWestTwoTwoFourZeroSouthMember
     
Accumulated depreciation 12/31/2012 966us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenTwoWestTwoTwoFourZeroSouthMember
     
1149 West 2240 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 217us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourNineWestTwoTwoFourZeroSouthMember
     
Building and Improvements 1,232us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourNineWestTwoTwoFourZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 325us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourNineWestTwoTwoFourZeroSouthMember
     
Land 225us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourNineWestTwoTwoFourZeroSouthMember
     
Building and improvements 1,549us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourNineWestTwoTwoFourZeroSouthMember
     
Total 1,774us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourNineWestTwoTwoFourZeroSouthMember
     
Accumulated depreciation 12/31/2012 620us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourNineWestTwoTwoFourZeroSouthMember
     
1142 West 2320 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 217us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourTwoWestTwoThreeTwoZeroSouthMember
     
Building and Improvements 1,232us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourTwoWestTwoThreeTwoZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 260us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourTwoWestTwoThreeTwoZeroSouthMember
     
Land 225us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourTwoWestTwoThreeTwoZeroSouthMember
     
Building and improvements 1,484us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourTwoWestTwoThreeTwoZeroSouthMember
     
Total 1,709us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourTwoWestTwoThreeTwoZeroSouthMember
     
Accumulated depreciation 12/31/2012 571us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFourTwoWestTwoThreeTwoZeroSouthMember
     
1152 West 2240 South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 1,652us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveTwoWestTwoTwoFourZeroSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,323us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveTwoWestTwoTwoFourZeroSouthMember
     
Land 669us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveTwoWestTwoTwoFourZeroSouthMember
     
Building and improvements 3,306us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveTwoWestTwoTwoFourZeroSouthMember
     
Total 3,975us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveTwoWestTwoTwoFourZeroSouthMember
     
Accumulated depreciation 12/31/2012 1,190us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneFiveTwoWestTwoTwoFourZeroSouthMember
     
2323 South 900 W [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Salt Lake City, UT      
Initial Cost of Land 886us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoThreeSouthNineZeroZeroWMember
     
Building and Improvements 2,995us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoThreeSouthNineZeroZeroWMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (3)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoThreeSouthNineZeroZeroWMember
     
Land 898us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoThreeSouthNineZeroZeroWMember
     
Building and improvements 2,980us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoThreeSouthNineZeroZeroWMember
     
Total 3,878us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoThreeSouthNineZeroZeroWMember
     
Accumulated depreciation 12/31/2012 1,388us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoThreeSouthNineZeroZeroWMember
     
1815-1957 South 4650 West [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Salt Lake City, UT      
Encumbrances 6,983us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
Initial Cost of Land 1,707us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
Building and Improvements 10,873us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 541us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
Land 1,713us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
Building and improvements 11,408us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
Total 13,121us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
Accumulated depreciation 12/31/2012 3,065us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightOneFiveToOneNineFiveSevenSouthFourSixFiveZeroWestMember
     
2100 Alexander Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 376us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneZeroZeroAlexanderStreetMember
     
Building and Improvements 1,670us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneZeroZeroAlexanderStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 319us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneZeroZeroAlexanderStreetMember
     
Land 376us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneZeroZeroAlexanderStreetMember
     
Building and improvements 1,989us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneZeroZeroAlexanderStreetMember
     
Total 2,365us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneZeroZeroAlexanderStreetMember
     
Accumulated depreciation 12/31/2012 518us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneZeroZeroAlexanderStreetMember
     
2064 Alexander Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) West Valley, UT      
Initial Cost of Land 864us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixFourAlexanderStreetMember
     
Building and Improvements 2,771us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixFourAlexanderStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 83us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixFourAlexanderStreetMember
     
Land 869us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixFourAlexanderStreetMember
     
Building and improvements 2,849us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixFourAlexanderStreetMember
     
Total 3,718us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixFourAlexanderStreetMember
     
Accumulated depreciation 12/31/2012 825us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixFourAlexanderStreetMember
     
1901 Raymond Ave SW [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Renton, WA      
Encumbrances 1,101us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
Initial Cost of Land 4,458us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
Building and Improvements 2,659us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 400us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
Land 4,594us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
Building and improvements 2,923us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
Total 7,517us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
Accumulated depreciation 12/31/2012 624us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneRaymondAvenueSwMember
     
19014 64th Avenue South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Kent, WA      
Encumbrances 3,063us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
Initial Cost of Land 1,990us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
Building and Improvements 3,979us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 514us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
Land 2,042us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
Building and improvements 4,441us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
Total 6,483us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
Accumulated depreciation 12/31/2012 1,116us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroOneFourSixFourAvenueSouthMember
     
18640 68th Avenue South [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Kent, WA      
Encumbrances 440us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
Initial Cost of Land 1,218us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
Building and Improvements 1,950us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 307us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
Land 1,258us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
Building and improvements 2,217us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
Total 3,475us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
Accumulated depreciation 12/31/2012 551us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightSixFourZeroSixEightAvenueSouthMember
     
1944 Vista Bella Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Encumbrances 3,620us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
Initial Cost of Land 1,746us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
Building and Improvements 3,148us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 465us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
Land 1,822us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
Building and improvements 3,537us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
Total 5,359us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
Accumulated depreciation 12/31/2012 1,298us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineFourFourVistaBellaWayMember
     
2000 Vista Bella Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Encumbrances 1,314us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
Initial Cost of Land 817us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
Building and Improvements 1,673us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 292us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
Land 853us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
Building and improvements 1,929us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
Total 2,782us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
Accumulated depreciation 12/31/2012 737us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroZeroZeroVistaBellaWayMember
     
2835 East Ana Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Encumbrances 3,105us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
Initial Cost of Land 1,682us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
Building and Improvements 2,750us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 339us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
Land 1,772us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
Building and improvements 2,999us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
Total 4,771us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
Accumulated depreciation 12/31/2012 963us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoEightThreeFiveEastAnaStreetMember
     
16275 Technology Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) San Diego, CA      
Initial Cost of Land 2,848us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoSevenFiveTechnologyDriveMember
     
Building and Improvements 8,641us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoSevenFiveTechnologyDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 527us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoSevenFiveTechnologyDriveMember
     
Land 2,859us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoSevenFiveTechnologyDriveMember
     
Building and improvements 9,157us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoSevenFiveTechnologyDriveMember
     
Total 12,016us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoSevenFiveTechnologyDriveMember
     
Accumulated depreciation 12/31/2012 2,359us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneSixTwoSevenFiveTechnologyDriveMember
     
8921- 8971 Fost Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hazelwood, MO      
Initial Cost of Land 431us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightNineTwoOneToEightNineSevenOneFostAvenueMember
     
Building and Improvements 2,479us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightNineTwoOneToEightNineSevenOneFostAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 818us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightNineTwoOneToEightNineSevenOneFostAvenueMember
     
Land 431us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightNineTwoOneToEightNineSevenOneFostAvenueMember
     
Building and improvements 3,297us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightNineTwoOneToEightNineSevenOneFostAvenueMember
     
Total 3,728us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightNineTwoOneToEightNineSevenOneFostAvenueMember
     
Accumulated depreciation 12/31/2012 1,456us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightNineTwoOneToEightNineSevenOneFostAvenueMember
     
9043-9083 Frost Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hazelwood, MO      
Initial Cost of Land 319us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroFourThreeToNineZeroEightThreeFrostAvenueMember
     
Building and Improvements 1,838us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroFourThreeToNineZeroEightThreeFrostAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,338us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroFourThreeToNineZeroEightThreeFrostAvenueMember
     
Land 319us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroFourThreeToNineZeroEightThreeFrostAvenueMember
     
Building and improvements 4,176us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroFourThreeToNineZeroEightThreeFrostAvenueMember
     
Total 4,495us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroFourThreeToNineZeroEightThreeFrostAvenueMember
     
Accumulated depreciation 12/31/2012 1,480us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroFourThreeToNineZeroEightThreeFrostAvenueMember
     
10431 Midwest Industrial Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Olivette, MO      
Encumbrances 1,446us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
Initial Cost of Land 237us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
Building and Improvements 1,360us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 745us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
Land 237us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
Building and improvements 2,105us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
Total 2,342us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
Accumulated depreciation 12/31/2012 875us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroFourThreeOneToOneZeroFourFourNineMidwestIndustrialBlvdMember
     
10751 Midwest Industrial Boulevard [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Olivette, MO      
Initial Cost of Land 193us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSevenFiveOneMidwestIndustrialBoulevardMember
     
Building and Improvements 1,119us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSevenFiveOneMidwestIndustrialBoulevardMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 294us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSevenFiveOneMidwestIndustrialBoulevardMember
     
Land 194us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSevenFiveOneMidwestIndustrialBoulevardMember
     
Building and improvements 1,412us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSevenFiveOneMidwestIndustrialBoulevardMember
     
Total 1,606us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSevenFiveOneMidwestIndustrialBoulevardMember
     
Accumulated depreciation 12/31/2012 584us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSevenFiveOneMidwestIndustrialBoulevardMember
     
6951 N Hanley [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Hazelwood, MO      
Initial Cost of Land 405us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneNHanleyDMember
     
Building and Improvements 2,295us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneNHanleyDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,577us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneNHanleyDMember
     
Land 419us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneNHanleyDMember
     
Building and improvements 4,858us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneNHanleyDMember
     
Total 5,277us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneNHanleyDMember
     
Accumulated depreciation 12/31/2012 1,839us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixNineFiveOneNHanleyDMember
     
1067-1083 Warson-Bldg A [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) St. Louis, MO      
Encumbrances 1,642us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
Initial Cost of Land 246us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
Building and Improvements 1,359us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 826us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
Land 251us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
Building and improvements 2,180us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
Total 2,431us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
Accumulated depreciation 12/31/2012 570us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroSixSevenToOneZeroEightThreeWarsonBuildingMember
     
1093-1107 Warson-Bldg B [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) St. Louis, MO      
Encumbrances 2,813us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
Initial Cost of Land 380us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
Building and Improvements 2,103us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,681us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
Land 388us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
Building and improvements 3,776us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
Total 4,164us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
Accumulated depreciation 12/31/2012 1,027us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroNineThreeToOneOneZeroSevenWarsonBuildingMember
     
1113-1129 Warson-Bldg C [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) St. Louis, MO      
Encumbrances 2,322us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
Initial Cost of Land 303us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
Building and Improvements 1,680us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,454us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
Land 310us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
Building and improvements 3,127us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
Total 3,437us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
Accumulated depreciation 12/31/2012 1,139us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneThreeToOneOneTwoNineWarsonBuildingMember
     
1131-1151 Warson-Bldg D [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) St. Louis, MO      
Encumbrances 2,198us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
Initial Cost of Land 353us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
Building and Improvements 1,952us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 949us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
Land 360us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
Building and improvements 2,894us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
Total 3,254us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
Accumulated depreciation 12/31/2012 766us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneThreeOneToOneOneFiveOneWarsonBuildingMember
     
6821-6857 Hazelwood Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Berkeley, MO      
Initial Cost of Land 985us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixEightTwoOneToSixEightFiveSevenHazelwoodAvenueMember
     
Building and Improvements 6,205us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixEightTwoOneToSixEightFiveSevenHazelwoodAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 908us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixEightTwoOneToSixEightFiveSevenHazelwoodAvenueMember
     
Land 985us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixEightTwoOneToSixEightFiveSevenHazelwoodAvenueMember
     
Building and improvements 7,113us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixEightTwoOneToSixEightFiveSevenHazelwoodAvenueMember
     
Total 8,098us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixEightTwoOneToSixEightFiveSevenHazelwoodAvenueMember
     
Accumulated depreciation 12/31/2012 2,090us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixEightTwoOneToSixEightFiveSevenHazelwoodAvenueMember
     
13701 Rider Trail North [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Earth City, MO      
Initial Cost of Land 800us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSevenZeroOneRiderTrailNorthMember
     
Building and Improvements 2,099us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSevenZeroOneRiderTrailNorthMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 710us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSevenZeroOneRiderTrailNorthMember
     
Land 804us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSevenZeroOneRiderTrailNorthMember
     
Building and improvements 2,805us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSevenZeroOneRiderTrailNorthMember
     
Total 3,609us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSevenZeroOneRiderTrailNorthMember
     
Accumulated depreciation 12/31/2012 1,025us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeSevenZeroOneRiderTrailNorthMember
     
1908-2000 Innerbelt [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Overland, MO      
Encumbrances 7,215us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
Initial Cost of Land 1,590us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
Building and Improvements 9,026us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,095us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
Land 1,591us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
Building and improvements 10,120us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
Total 11,711us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
Accumulated depreciation 12/31/2012 3,741us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroEightToTwoZeroZeroZeroInnerbeltDMember
     
9060 Latty Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Berkeley, MO      
Initial Cost of Land 687us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroSixZeroLattyAvenueMember
     
Building and Improvements 1,947us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroSixZeroLattyAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (90)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroSixZeroLattyAvenueMember
     
Land 694us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroSixZeroLattyAvenueMember
     
Building and improvements 1,850us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroSixZeroLattyAvenueMember
     
Total 2,544us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroSixZeroLattyAvenueMember
     
Accumulated depreciation 12/31/2012 1,554us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineZeroSixZeroLattyAvenueMember
     
21-25 Gateway Commerce Center [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Edwardsville, IL      
Initial Cost of Land 1,874us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneToTwoFiveGatewayCommerceCenterMember
     
Building and Improvements 31,958us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneToTwoFiveGatewayCommerceCenterMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (331)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneToTwoFiveGatewayCommerceCenterMember
     
Land 1,902us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneToTwoFiveGatewayCommerceCenterMember
     
Building and improvements 31,599us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneToTwoFiveGatewayCommerceCenterMember
     
Total 33,501us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneToTwoFiveGatewayCommerceCenterMember
     
Accumulated depreciation 12/31/2012 7,272us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneToTwoFiveGatewayCommerceCenterMember
     
6647 Romiss Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) St. Louis, MO      
Initial Cost of Land 230us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFourSevenRomissCourtMember
     
Building and Improvements 681us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFourSevenRomissCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (8)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFourSevenRomissCourtMember
     
Land 241us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFourSevenRomissCourtMember
     
Building and improvements 662us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFourSevenRomissCourtMember
     
Total 903us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFourSevenRomissCourtMember
     
Accumulated depreciation 12/31/2012 245us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFourSevenRomissCourtMember
     
5313 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 204us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeOneThreeJohnsRoadMember
     
Building and Improvements 1,159us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeOneThreeJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 573us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeOneThreeJohnsRoadMember
     
Land 257us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeOneThreeJohnsRoadMember
     
Building and improvements 1,679us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeOneThreeJohnsRoadMember
     
Total 1,936us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeOneThreeJohnsRoadMember
     
Accumulated depreciation 12/31/2012 640us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveThreeOneThreeJohnsRoadMember
     
5525 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 192us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveTwoFiveJohnsRoadMember
     
Building and Improvements 1,086us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveTwoFiveJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 294us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveTwoFiveJohnsRoadMember
     
Land 200us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveTwoFiveJohnsRoadMember
     
Building and improvements 1,372us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveTwoFiveJohnsRoadMember
     
Total 1,572us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveTwoFiveJohnsRoadMember
     
Accumulated depreciation 12/31/2012 539us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveTwoFiveJohnsRoadMember
     
5709 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 192us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroNineJohnsRoadMember
     
Building and Improvements 1,086us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroNineJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 197us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroNineJohnsRoadMember
     
Land 200us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroNineJohnsRoadMember
     
Building and improvements 1,275us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroNineJohnsRoadMember
     
Total 1,475us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroNineJohnsRoadMember
     
Accumulated depreciation 12/31/2012 534us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenZeroNineJohnsRoadMember
     
5711 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 243us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenOneOneJohnsRoadMember
     
Building and Improvements 1,376us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenOneOneJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 159us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenOneOneJohnsRoadMember
     
Land 255us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenOneOneJohnsRoadMember
     
Building and improvements 1,523us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenOneOneJohnsRoadMember
     
Total 1,778us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenOneOneJohnsRoadMember
     
Accumulated depreciation 12/31/2012 640us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveSevenOneOneJohnsRoadMember
     
5453 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 71us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveThreeWWatersAvenueMember
     
Building and Improvements 402us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveThreeWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 163us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveThreeWWatersAvenueMember
     
Land 82us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveThreeWWatersAvenueMember
     
Building and improvements 554us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveThreeWWatersAvenueMember
     
Total 636us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveThreeWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 236us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveThreeWWatersAvenueMember
     
5455 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 307us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveFiveWWatersAvenueMember
     
Building and Improvements 1,742us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveFiveWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 747us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveFiveWWatersAvenueMember
     
Land 326us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveFiveWWatersAvenueMember
     
Building and improvements 2,470us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveFiveWWatersAvenueMember
     
Total 2,796us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveFiveWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 1,043us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourFiveFiveWWatersAvenueMember
     
5553 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 307us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveThreeWWatersAvenueMember
     
Building and Improvements 1,742us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveThreeWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 417us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveThreeWWatersAvenueMember
     
Land 326us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveThreeWWatersAvenueMember
     
Building and improvements 2,140us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveThreeWWatersAvenueMember
     
Total 2,466us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveThreeWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 885us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveThreeWWatersAvenueMember
     
5501 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 215us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroOneWWatersAvenueMember
     
Building and Improvements 871us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroOneWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 298us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroOneWWatersAvenueMember
     
Land 242us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroOneWWatersAvenueMember
     
Building and improvements 1,142us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroOneWWatersAvenueMember
     
Total 1,384us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroOneWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 491us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroOneWWatersAvenueMember
     
5503 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 98us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroThreeWWatersAvenueMember
     
Building and Improvements 402us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroThreeWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 328us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroThreeWWatersAvenueMember
     
Land 110us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroThreeWWatersAvenueMember
     
Building and improvements 718us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroThreeWWatersAvenueMember
     
Total 828us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroThreeWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 374us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveZeroThreeWWatersAvenueMember
     
5555 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 213us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveWWatersAvenueMember
     
Building and Improvements 1,206us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 230us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveWWatersAvenueMember
     
Land 221us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveWWatersAvenueMember
     
Building and improvements 1,428us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveWWatersAvenueMember
     
Total 1,649us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 625us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveWWatersAvenueMember
     
5557 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 59us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveSevenWWatersAvenueMember
     
Building and Improvements 335us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveSevenWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 59us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveSevenWWatersAvenueMember
     
Land 62us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveSevenWWatersAvenueMember
     
Building and improvements 391us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveSevenWWatersAvenueMember
     
Total 453us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveSevenWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 160us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveSevenWWatersAvenueMember
     
5463 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 497us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixThreeWWatersAvenueMember
     
Building and Improvements 2,751us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixThreeWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 694us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixThreeWWatersAvenueMember
     
Land 560us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixThreeWWatersAvenueMember
     
Building and improvements 3,382us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixThreeWWatersAvenueMember
     
Total 3,942us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixThreeWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 1,371us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixThreeWWatersAvenueMember
     
5461 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 261us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixOneWWatersMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,355us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixOneWWatersMember
     
Land 265us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixOneWWatersMember
     
Building and improvements 1,351us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixOneWWatersMember
     
Total 1,616us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixOneWWatersMember
     
Accumulated depreciation 12/31/2012 541us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourSixOneWWatersMember
     
5481 W Waters Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 558us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourEightOneWWatersAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,263us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourEightOneWWatersAvenueMember
     
Land 561us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourEightOneWWatersAvenueMember
     
Building and improvements 2,260us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourEightOneWWatersAvenueMember
     
Total 2,821us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourEightOneWWatersAvenueMember
     
Accumulated depreciation 12/31/2012 832us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFourEightOneWWatersAvenueMember
     
4515-4519 George Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 633us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveToFourFiveOneNineGeorgeRoadMember
     
Building and Improvements 3,587us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveToFourFiveOneNineGeorgeRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 854us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveToFourFiveOneNineGeorgeRoadMember
     
Land 640us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveToFourFiveOneNineGeorgeRoadMember
     
Building and improvements 4,434us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveToFourFiveOneNineGeorgeRoadMember
     
Total 5,074us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveToFourFiveOneNineGeorgeRoadMember
     
Accumulated depreciation 12/31/2012 1,526us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourFiveOneFiveToFourFiveOneNineGeorgeRoadMember
     
6089 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 180us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroEightNineJohnsRoadMember
     
Building and Improvements 987us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroEightNineJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroEightNineJohnsRoadMember
     
Land 186us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroEightNineJohnsRoadMember
     
Building and improvements 983us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroEightNineJohnsRoadMember
     
Total 1,169us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroEightNineJohnsRoadMember
     
Accumulated depreciation 12/31/2012 320us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroEightNineJohnsRoadMember
     
6091 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 140us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroNineOneJohnsRoadMember
     
Building and Improvements 730us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroNineOneJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (32)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroNineOneJohnsRoadMember
     
Land 144us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroNineOneJohnsRoadMember
     
Building and improvements 694us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroNineOneJohnsRoadMember
     
Total 838us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroNineOneJohnsRoadMember
     
Accumulated depreciation 12/31/2012 219us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroNineOneJohnsRoadMember
     
6103 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 220us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroThreeJohnsRoadMember
     
Building and Improvements 1,160us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroThreeJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 16us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroThreeJohnsRoadMember
     
Land 226us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroThreeJohnsRoadMember
     
Building and improvements 1,170us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroThreeJohnsRoadMember
     
Total 1,396us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroThreeJohnsRoadMember
     
Accumulated depreciation 12/31/2012 387us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroThreeJohnsRoadMember
     
6201 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 200us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneJohnsRoadMember
     
Building and Improvements 1,107us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneJohnsRoadMember
     
Land 205us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneJohnsRoadMember
     
Building and improvements 1,105us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneJohnsRoadMember
     
Total 1,310us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneJohnsRoadMember
     
Accumulated depreciation 12/31/2012 415us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroOneJohnsRoadMember
     
6203 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 300us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroThreeJohnsRoadMember
     
Building and Improvements 1,460us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroThreeJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (311)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroThreeJohnsRoadMember
     
Land 311us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroThreeJohnsRoadMember
     
Building and improvements 1,138us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroThreeJohnsRoadMember
     
Total 1,449us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroThreeJohnsRoadMember
     
Accumulated depreciation 12/31/2012 348us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroThreeJohnsRoadMember
     
6205 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 270us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroFiveJohnsRoadMember
     
Building and Improvements 1,363us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroFiveJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 152us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroFiveJohnsRoadMember
     
Land 278us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroFiveJohnsRoadMember
     
Building and improvements 1,507us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroFiveJohnsRoadMember
     
Total 1,785us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroFiveJohnsRoadMember
     
Accumulated depreciation 12/31/2012 445us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoZeroFiveJohnsRoadMember
     
6101 Johns Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 210us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroOneJohnsRoadMember
     
Building and Improvements 833us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroOneJohnsRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 49us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroOneJohnsRoadMember
     
Land 216us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroOneJohnsRoadMember
     
Building and improvements 876us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroOneJohnsRoadMember
     
Total 1,092us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroOneJohnsRoadMember
     
Accumulated depreciation 12/31/2012 304us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneZeroOneJohnsRoadMember
     
4908 Tampa West Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Tampa, FL      
Initial Cost of Land 2,622us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroEightTampaWestBlvdMember
     
Building and Improvements 8,643us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroEightTampaWestBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (820)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroEightTampaWestBlvdMember
     
Land 2,635us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroEightTampaWestBlvdMember
     
Building and improvements 7,810us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroEightTampaWestBlvdMember
     
Total 10,445us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroEightTampaWestBlvdMember
     
Accumulated depreciation 12/31/2012 2,722us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroEightTampaWestBlvdMember
     
7201-7281 Bryan Dairy Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Largo, FL      
Initial Cost of Land 1,895us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoZeroOneToSevenTwoFourFiveBryanDairyRoadDMember
     
Building and Improvements 5,408us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoZeroOneToSevenTwoFourFiveBryanDairyRoadDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (1,552)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoZeroOneToSevenTwoFourFiveBryanDairyRoadDMember
     
Land 1,365us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoZeroOneToSevenTwoFourFiveBryanDairyRoadDMember
     
Building and improvements 4,386us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoZeroOneToSevenTwoFourFiveBryanDairyRoadDMember
     
Total 5,751us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoZeroOneToSevenTwoFourFiveBryanDairyRoadDMember
     
Accumulated depreciation 12/31/2012 1,129us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenTwoZeroOneToSevenTwoFourFiveBryanDairyRoadDMember
     
4900- 4914 Creekside Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Clearwater, FL      
Initial Cost of Land 3,702us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroZeroToFourNineOneFourCreeksideDriveHMember
     
Building and Improvements 7,338us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroZeroToFourNineOneFourCreeksideDriveHMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (3,486)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroZeroToFourNineOneFourCreeksideDriveHMember
     
Land 2,245us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroZeroToFourNineOneFourCreeksideDriveHMember
     
Building and improvements 5,309us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroZeroToFourNineOneFourCreeksideDriveHMember
     
Total 7,554us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroZeroToFourNineOneFourCreeksideDriveHMember
     
Accumulated depreciation 12/31/2012 1,787us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourNineZeroZeroToFourNineOneFourCreeksideDriveHMember
     
12345 Starkey Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Largo, FL      
Initial Cost of Land 898us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoThreeFourFiveStarkeyRoadMember
     
Building and Improvements 2,078us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoThreeFourFiveStarkeyRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (629)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoThreeFourFiveStarkeyRoadMember
     
Land 599us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoThreeFourFiveStarkeyRoadMember
     
Building and improvements 1,748us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoThreeFourFiveStarkeyRoadMember
     
Total 2,347us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoThreeFourFiveStarkeyRoadMember
     
Accumulated depreciation 12/31/2012 651us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoThreeFourFiveStarkeyRoadMember
     
5050 Kendrick Court [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Rapids, MI      
Initial Cost of Land 1,721us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroKendrickCourtMember
     
Building and Improvements 11,433us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroKendrickCourtMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (2,272)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroKendrickCourtMember
     
Land 988us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroKendrickCourtMember
     
Building and improvements 9,894us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroKendrickCourtMember
     
Total 10,882us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroKendrickCourtMember
     
Accumulated depreciation 12/31/2012 7,264us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveZeroFiveZeroKendrickCourtMember
     
2250 Delaware Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Des Moines, IA      
Initial Cost of Land 277us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoFiveZeroDelawareAvenueMember
     
Building and Improvements 1,609us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoFiveZeroDelawareAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (133)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoFiveZeroDelawareAvenueMember
     
Land 173us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoFiveZeroDelawareAvenueMember
     
Building and improvements 1,580us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoFiveZeroDelawareAvenueMember
     
Total 1,753us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoFiveZeroDelawareAvenueMember
     
Accumulated depreciation 12/31/2012 743us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoTwoFiveZeroDelawareAvenueMember
     
9601A Dessau Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Austin, TX      
Encumbrances 1,187us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneDessauRoadMember
     
Initial Cost of Land 255us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneDessauRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,893us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneDessauRoadMember
     
Land 366us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneDessauRoadMember
     
Building and improvements 1,782us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneDessauRoadMember
     
Total 2,148us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneDessauRoadMember
     
Accumulated depreciation 12/31/2012 711us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneDessauRoadMember
     
9601C Dessau Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Austin, TX      
Encumbrances 1,418us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneCDessauRoadMember
     
Initial Cost of Land 248us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneCDessauRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 2,319us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneCDessauRoadMember
     
Land 355us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneCDessauRoadMember
     
Building and improvements 2,212us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneCDessauRoadMember
     
Total 2,567us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneCDessauRoadMember
     
Accumulated depreciation 12/31/2012 1,089us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneCDessauRoadMember
     
9601B Dessau Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Austin, TX      
Encumbrances 1,177us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneBDessauRoadMember
     
Initial Cost of Land 248us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneBDessauRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,883us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneBDessauRoadMember
     
Land 355us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneBDessauRoadMember
     
Building and improvements 1,776us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneBDessauRoadMember
     
Total 2,131us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneBDessauRoadMember
     
Accumulated depreciation 12/31/2012 652us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_NineSixZeroOneBDessauRoadMember
     
6266 Hurt Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Horn Lake, MS      
Initial Cost of Land 427us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoSixSixHurtRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 3,712us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoSixSixHurtRoadMember
     
Land 387us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoSixSixHurtRoadMember
     
Building and improvements 3,752us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoSixSixHurtRoadMember
     
Total 4,139us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoSixSixHurtRoadMember
     
Accumulated depreciation 12/31/2012 836us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixTwoSixSixHurtRoadMember
     
665 N. Baldwin Park Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) City of Industry, CA      
Encumbrances 4,226us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
Initial Cost of Land 2,124us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
Building and Improvements 5,219us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,601us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
Land 2,143us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
Building and improvements 6,801us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
Total 8,944us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
Accumulated depreciation 12/31/2012 2,477us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixSixFiveNBaldwinParkBlvdMember
     
27801 Avenue Scott [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Santa Clarita, CA      
Encumbrances 7,228us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
Initial Cost of Land 2,890us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
Building and Improvements 7,020us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 788us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
Land 2,902us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
Building and improvements 7,796us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
Total 10,698us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
Accumulated depreciation 12/31/2012 2,377us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSevenEightZeroOneAvenueScottMember
     
2610 & 2660 Columbia [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Torrance, CA      
Encumbrances 4,524us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
Initial Cost of Land 3,008us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
Building and Improvements 5,826us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 740us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
Land 3,031us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
Building and improvements 6,543us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
Total 9,574us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
Accumulated depreciation 12/31/2012 1,770us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoSixOneZeroAndTwoSixSixZeroColumbiaMember
     
433 Alaska Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Torrance, CA      
Initial Cost of Land 681us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeThreeAlaskaAvenueMember
     
Building and Improvements 168us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeThreeAlaskaAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (5)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeThreeAlaskaAvenueMember
     
Land 684us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeThreeAlaskaAvenueMember
     
Building and improvements 160us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeThreeAlaskaAvenueMember
     
Total 844us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeThreeAlaskaAvenueMember
     
Accumulated depreciation 12/31/2012 85us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThreeThreeAlaskaAvenueMember
     
4020 S. Compton Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Los Angeles, CA      
Initial Cost of Land 3,800us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroTwoZeroSComptonAvenueMember
     
Building and Improvements 7,330us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroTwoZeroSComptonAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (233)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroTwoZeroSComptonAvenueMember
     
Land 3,825us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroTwoZeroSComptonAvenueMember
     
Building and improvements 7,072us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroTwoZeroSComptonAvenueMember
     
Total 10,897us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroTwoZeroSComptonAvenueMember
     
Accumulated depreciation 12/31/2012 1,716us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourZeroTwoZeroSComptonAvenueMember
     
6305 El Camino Real [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Initial Cost of Land 1,590us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroFiveElCaminoRealMember
     
Building and Improvements 6,360us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroFiveElCaminoRealMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 7,730us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroFiveElCaminoRealMember
     
Land 1,590us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroFiveElCaminoRealMember
     
Building and improvements 14,090us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroFiveElCaminoRealMember
     
Total 15,680us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroFiveElCaminoRealMember
     
Accumulated depreciation 12/31/2012 3,419us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroFiveElCaminoRealMember
     
2325 Camino Vida Roble [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Encumbrances 1,954us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
Initial Cost of Land 1,441us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
Building and Improvements 1,239us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 627us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
Land 1,446us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
Building and improvements 1,861us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
Total 3,307us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
Accumulated depreciation 12/31/2012 458us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeTwoFiveCaminoVidaRobleMember
     
2335 Camino Vida Roble [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Encumbrances 1,055us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
Initial Cost of Land 817us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
Building and Improvements 762us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 207us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
Land 821us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
Building and improvements 965us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
Total 1,786us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
Accumulated depreciation 12/31/2012 350us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeThreeFiveCaminoVidaRobleMember
     
2345 Camino Vida Roble [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Encumbrances 681us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
Initial Cost of Land 562us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
Building and Improvements 456us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 51us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
Land 565us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
Building and improvements 504us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
Total 1,069us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
Accumulated depreciation 12/31/2012 224us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFourFiveCaminoVidaRobleMember
     
2355 Camino Vida Roble [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Encumbrances 640us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
Initial Cost of Land 481us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
Building and Improvements 365us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 237us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
Land 483us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
Building and improvements 600us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
Total 1,083us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
Accumulated depreciation 12/31/2012 171us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeFiveFiveCaminoVidaRobleMember
     
2365 Camino Vida Roble [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Encumbrances 1,212us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
Initial Cost of Land 1,098us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
Building and Improvements 630us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 323us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
Land 1,102us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
Building and improvements 949us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
Total 2,051us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
Accumulated depreciation 12/31/2012 273us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSixFiveCaminoVidaRobleMember
     
2375 Camino Vida Roble [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Encumbrances 1,326us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
Initial Cost of Land 1,210us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
Building and Improvements 874us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 96us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
Land 1,214us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
Building and improvements 966us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
Total 2,180us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
Accumulated depreciation 12/31/2012 323us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeSevenFiveCaminoVidaRobleMember
     
6451 El Camino Real [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Carlsbad, CA      
Initial Cost of Land 2,885us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveOneElCaminoRealMember
     
Building and Improvements 1,931us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveOneElCaminoRealMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 623us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveOneElCaminoRealMember
     
Land 2,895us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveOneElCaminoRealMember
     
Building and improvements 2,544us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveOneElCaminoRealMember
     
Total 5,439us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveOneElCaminoRealMember
     
Accumulated depreciation 12/31/2012 802us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixFourFiveOneElCaminoRealMember
     
8572 Spectrum Lane [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) San Diego, CA      
Encumbrances 2,034us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
Initial Cost of Land 806us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
Building and Improvements 3,225us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 274us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
Land 807us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
Building and improvements 3,498us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
Total 4,305us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
Accumulated depreciation 12/31/2012 680us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightFiveSevenTwoSpectrumLaneMember
     
13100 Gregg Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Poway, CA      
Initial Cost of Land 1,040us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeOneZeroZeroGreggStreetMember
     
Building and Improvements 4,160us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeOneZeroZeroGreggStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 509us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeOneZeroZeroGreggStreetMember
     
Land 1,073us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeOneZeroZeroGreggStreetMember
     
Building and improvements 4,636us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeOneZeroZeroGreggStreetMember
     
Total 5,709us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeOneZeroZeroGreggStreetMember
     
Accumulated depreciation 12/31/2012 1,353us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneThreeOneZeroZeroGreggStreetMember
     
21730-21748 Marilla St. [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Chatsworth, CA      
Encumbrances 2,766us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
Initial Cost of Land 2,585us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
Building and Improvements 3,210us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 58us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
Land 2,608us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
Building and improvements 3,245us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
Total 5,853us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
Accumulated depreciation 12/31/2012 912us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoOneSevenThreeZeroToTwoOneSevenFourEightMarillaStMember
     
8015 Paramount [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pico Rivera, CA      
Initial Cost of Land 3,616us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneFiveParamountMember
     
Building and Improvements 3,902us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneFiveParamountMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 61us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneFiveParamountMember
     
Land 3,657us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneFiveParamountMember
     
Building and improvements 3,922us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneFiveParamountMember
     
Total 7,579us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneFiveParamountMember
     
Accumulated depreciation 12/31/2012 1,395us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_EightZeroOneFiveParamountMember
     
3365 E. Slauson [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Vernon, CA      
Initial Cost of Land 2,367us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveESlausonMember
     
Building and Improvements 3,243us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveESlausonMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 40us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveESlausonMember
     
Land 2,396us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveESlausonMember
     
Building and improvements 3,254us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveESlausonMember
     
Total 5,650us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveESlausonMember
     
Accumulated depreciation 12/31/2012 1,219us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThreeSixFiveESlausonMember
     
3015 East Ana [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Initial Cost of Land 19,678us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneFiveEastAnaMember
     
Building and Improvements 9,321us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneFiveEastAnaMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 6,305us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneFiveEastAnaMember
     
Land 20,144us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneFiveEastAnaMember
     
Building and improvements 15,160us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneFiveEastAnaMember
     
Total 35,304us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneFiveEastAnaMember
     
Accumulated depreciation 12/31/2012 3,470us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroOneFiveEastAnaMember
     
19067 Reyes Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Initial Cost of Land 9,281us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroSixSevenReyesAvenueMember
     
Building and Improvements 3,920us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroSixSevenReyesAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 102us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroSixSevenReyesAvenueMember
     
Land 9,381us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroSixSevenReyesAvenueMember
     
Building and improvements 3,922us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroSixSevenReyesAvenueMember
     
Total 13,303us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroSixSevenReyesAvenueMember
     
Accumulated depreciation 12/31/2012 1,557us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroSixSevenReyesAvenueMember
     
24870 Nandina Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Moreno Valley, CA      
Initial Cost of Land 13,543us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightSevenZeroNandinaAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 20,885us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightSevenZeroNandinaAvenueMember
     
Land 6,482us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightSevenZeroNandinaAvenueMember
     
Building and improvements 27,946us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightSevenZeroNandinaAvenueMember
     
Total 34,428us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightSevenZeroNandinaAvenueMember
     
Accumulated depreciation 12/31/2012 1,627us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoFourEightSevenZeroNandinaAvenueMember
     
1250 Rancho Conejo Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thousand Oaks, CA      
Initial Cost of Land 1,435us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveZeroRanchoConejoBlvdMember
     
Building and Improvements 779us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveZeroRanchoConejoBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 42us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveZeroRanchoConejoBlvdMember
     
Land 1,441us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveZeroRanchoConejoBlvdMember
     
Building and improvements 815us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveZeroRanchoConejoBlvdMember
     
Total 2,256us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveZeroRanchoConejoBlvdMember
     
Accumulated depreciation 12/31/2012 331us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoFiveZeroRanchoConejoBlvdMember
     
1260 Rancho Conejo Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thousand Oaks, CA      
Initial Cost of Land 1,353us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroRanchoConejoBlvdMember
     
Building and Improvements 722us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroRanchoConejoBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (844)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroRanchoConejoBlvdMember
     
Land 675us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroRanchoConejoBlvdMember
     
Building and improvements 556us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroRanchoConejoBlvdMember
     
Total 1,231us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroRanchoConejoBlvdMember
     
Accumulated depreciation 12/31/2012 232us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixZeroRanchoConejoBlvdMember
     
1270 Rancho Conejo Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thousand Oaks, CA      
Initial Cost of Land 1,224us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroRanchoConejoBlvdMember
     
Building and Improvements 716us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroRanchoConejoBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 21us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroRanchoConejoBlvdMember
     
Land 1,229us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroRanchoConejoBlvdMember
     
Building and improvements 732us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroRanchoConejoBlvdMember
     
Total 1,961us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroRanchoConejoBlvdMember
     
Accumulated depreciation 12/31/2012 305us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSevenZeroRanchoConejoBlvdMember
     
1280 Rancho Conejo Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thousand Oaks, CA      
Encumbrances 2,861us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
Initial Cost of Land 2,043us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
Building and Improvements 3,408us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (114)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
Land 2,051us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
Building and improvements 3,286us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
Total 5,337us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
Accumulated depreciation 12/31/2012 682us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoEightZeroRanchoConejoBlvdMember
     
1290 Rancho Conejo Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thousand Oaks, CA      
Encumbrances 2,416us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
Initial Cost of Land 1,754us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
Building and Improvements 2,949us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (204)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
Land 1,761us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
Building and improvements 2,738us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
Total 4,499us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
Accumulated depreciation 12/31/2012 594us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineZeroRanchoConejoBlvdMember
     
100 West Sinclair Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Riverside, CA      
Initial Cost of Land 4,894us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroWestSinclairMember
     
Building and Improvements 3,481us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroWestSinclairMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (5,233)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroWestSinclairMember
     
Land 1,819us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroWestSinclairMember
     
Building and improvements 1,323us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroWestSinclairMember
     
Total 3,142us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroWestSinclairMember
     
Accumulated depreciation 12/31/2012 540us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroZeroWestSinclairMember
     
14050 Day Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Moreno Valley, CA      
Encumbrances 3,313us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
Initial Cost of Land 2,538us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
Building and Improvements 2,538us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 291us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
Land 2,565us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
Building and improvements 2,801us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
Total 5,366us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
Accumulated depreciation 12/31/2012 779us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneFourZeroFiveZeroDayStreetMember
     
12925 Marlay Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Fontana, CA      
Encumbrances 9,092us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
Initial Cost of Land 6,072us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
Building and Improvements 7,891us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 762us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
Land 6,090us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
Building and improvements 8,635us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
Total 14,725us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
Accumulated depreciation 12/31/2012 3,159us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoNineTwoFiveMarlayAvenueMember
     
18201-18291 Santa Fe [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Encumbrances 9,708us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoZeroOneToOneEightTwoNineOneSantaFeMember
     
Initial Cost of Land 6,720us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoZeroOneToOneEightTwoNineOneSantaFeMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 9,004us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoZeroOneToOneEightTwoNineOneSantaFeMember
     
Land 6,897us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoZeroOneToOneEightTwoNineOneSantaFeMember
     
Building and improvements 8,827us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoZeroOneToOneEightTwoNineOneSantaFeMember
     
Total 15,724us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoZeroOneToOneEightTwoNineOneSantaFeMember
     
Accumulated depreciation 12/31/2012 1,636us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightTwoZeroOneToOneEightTwoNineOneSantaFeMember
     
1011 Rancho Conejo [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thousand Oaks, CA      
Encumbrances 5,328us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
Initial Cost of Land 7,717us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
Building and Improvements 2,518us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (155)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
Land 7,752us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
Building and improvements 2,327us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
Total 10,079us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
Accumulated depreciation 12/31/2012 1,000us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneOneRanchoConejoMember
     
2300 Corporate Center Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Thousand Oaks, CA      
Initial Cost of Land 6,506us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroCorporateCenterDriveMember
     
Building and Improvements 4,885us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroCorporateCenterDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (5,427)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroCorporateCenterDriveMember
     
Land 3,236us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroCorporateCenterDriveMember
     
Building and improvements 2,728us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroCorporateCenterDriveMember
     
Total 5,964us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroCorporateCenterDriveMember
     
Accumulated depreciation 12/31/2012 901us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoThreeZeroZeroCorporateCenterDriveMember
     
20700 Denker Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Encumbrances   5,280us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
   
Initial Cost of Land 5,767us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
     
Building and Improvements 2,538us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,282us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
     
Land 5,964us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
     
Building and improvements 3,624us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
     
Total 9,588us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
     
Accumulated depreciation 12/31/2012 1,433us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSevenZeroZeroDenkerAvenueMember
     
18408 Laurel Park Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Initial Cost of Land 2,850us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightFourZeroEightLaurelParkRoadMember
     
Building and Improvements 2,850us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightFourZeroEightLaurelParkRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 722us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightFourZeroEightLaurelParkRoadMember
     
Land 2,874us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightFourZeroEightLaurelParkRoadMember
     
Building and improvements 3,548us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightFourZeroEightLaurelParkRoadMember
     
Total 6,422us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightFourZeroEightLaurelParkRoadMember
     
Accumulated depreciation 12/31/2012 879us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneEightFourZeroEightLaurelParkRoadMember
     
19021 S. Reyes Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Rancho Dominguez, CA      
Initial Cost of Land 8,183us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroTwoOneSReyesAvenueMember
     
Building and Improvements 7,501us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroTwoOneSReyesAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 761us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroTwoOneSReyesAvenueMember
     
Land 8,545us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroTwoOneSReyesAvenueMember
     
Building and improvements 7,900us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroTwoOneSReyesAvenueMember
     
Total 16,445us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroTwoOneSReyesAvenueMember
     
Accumulated depreciation 12/31/2012 1,675us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneNineZeroTwoOneSReyesAvenueMember
     
Six One Eight Five Kimball Ave [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Chino, CA      
Initial Cost of Land 6,385us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneEightFiveKimballAveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 12,343us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneEightFiveKimballAveMember
     
Land 6,382us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneEightFiveKimballAveMember
     
Building and improvements 12,346us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneEightFiveKimballAveMember
     
Total 18,728us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneEightFiveKimballAveMember
     
Accumulated depreciation 12/31/2012 796us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixOneEightFiveKimballAveMember
     
Five Five Five Five Bandini Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Bell, CA      
Initial Cost of Land 32,536us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveBandiniBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 20,917us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveBandiniBlvdMember
     
Land 32,540us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveBandiniBlvdMember
     
Building and improvements 20,913us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveBandiniBlvdMember
     
Total 53,453us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveBandiniBlvdMember
     
Accumulated depreciation 12/31/2012 647us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveFiveFiveFiveBandiniBlvdMember
     
Sixteen Thousand Eight Hundred Seventy Five Heacock Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Moreno Valley, CA      
Building and Improvements 6,831us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandEightHundredSeventyFiveHeacockStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 72us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandEightHundredSeventyFiveHeacockStreetMember
     
Building and improvements 6,903us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandEightHundredSeventyFiveHeacockStreetMember
     
Total 6,903us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandEightHundredSeventyFiveHeacockStreetMember
     
Accumulated depreciation 12/31/2012 253us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixteenThousandEightHundredSeventyFiveHeacockStreetMember
     
Four Thousand Seven Hundred Ten Guasti Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Ontario, CA      
Initial Cost of Land 2,846us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTenGuastiRoadMember
     
Building and Improvements 6,564us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTenGuastiRoadMember
     
Land 2,846us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTenGuastiRoadMember
     
Building and improvements 6,564us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTenGuastiRoadMember
     
Total 9,410us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTenGuastiRoadMember
     
Accumulated depreciation 12/31/2012 41us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FourThousandSevenHundredTenGuastiRoadMember
     
Seventeen Thousand One Hundred Perris Boulevard [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Moreno Valley, CA      
Initial Cost of Land 6,388us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneHundredPerrisBoulevardMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 22,595us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneHundredPerrisBoulevardMember
     
Land 6,395us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneHundredPerrisBoulevardMember
     
Building and improvements 22,588us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneHundredPerrisBoulevardMember
     
Total 28,983us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneHundredPerrisBoulevardMember
     
Accumulated depreciation 12/31/2012 356us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SeventeenThousandOneHundredPerrisBoulevardMember
     
Thirteen Thousand Four Hundred Fourteen South Figueroa [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Los Angeles, CA      
Initial Cost of Land 1,701us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenThousandFourHundredFourteenSouthFigueroaMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 6,577us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenThousandFourHundredFourteenSouthFigueroaMember
     
Land 1,887us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenThousandFourHundredFourteenSouthFigueroaMember
     
Building and improvements 6,391us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenThousandFourHundredFourteenSouthFigueroaMember
     
Total 8,278us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenThousandFourHundredFourteenSouthFigueroaMember
     
Accumulated depreciation 12/31/2012 88us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThirteenThousandFourHundredFourteenSouthFigueroaMember
     
2060 Springdale Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Cherry Hill, NJ      
Initial Cost of Land 258us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixZeroSpringdaleRoadMember
     
Building and Improvements 1,436us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixZeroSpringdaleRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 625us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixZeroSpringdaleRoadMember
     
Land 258us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixZeroSpringdaleRoadMember
     
Building and improvements 2,061us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixZeroSpringdaleRoadMember
     
Total 2,319us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixZeroSpringdaleRoadMember
     
Accumulated depreciation 12/31/2012 808us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_TwoZeroSixZeroSpringdaleRoadMember
     
111 Whittendale Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Morrestown, NJ      
Initial Cost of Land 522us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneWhittendaleDriveMember
     
Building and Improvements 2,916us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneWhittendaleDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 519us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneWhittendaleDriveMember
     
Land 522us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneWhittendaleDriveMember
     
Building and improvements 3,435us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneWhittendaleDriveMember
     
Total 3,957us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneWhittendaleDriveMember
     
Accumulated depreciation 12/31/2012 1,217us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneOneWhittendaleDriveMember
     
7851 Airport Highway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pennsauken, NJ      
Initial Cost of Land 160us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightFiveOneAirportHighwayMember
     
Building and Improvements 508us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightFiveOneAirportHighwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 381us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightFiveOneAirportHighwayMember
     
Land 162us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightFiveOneAirportHighwayMember
     
Building and improvements 887us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightFiveOneAirportHighwayMember
     
Total 1,049us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightFiveOneAirportHighwayMember
     
Accumulated depreciation 12/31/2012 352us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightFiveOneAirportHighwayMember
     
103 Central Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Mt. Laurel, NJ      
Initial Cost of Land 610us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeCentralMember
     
Building and Improvements 1,847us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeCentralMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 1,471us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeCentralMember
     
Land 619us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeCentralMember
     
Building and improvements 3,309us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeCentralMember
     
Total 3,928us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeCentralMember
     
Accumulated depreciation 12/31/2012 1,085us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroThreeCentralMember
     
7890 Airport Hwy/7015 Central [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Pennsauken, NJ      
Initial Cost of Land 300us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightNineZeroAirportHighwaySevenZeroOneFiveCentralMember
     
Building and Improvements 989us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightNineZeroAirportHighwaySevenZeroOneFiveCentralMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 543us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightNineZeroAirportHighwaySevenZeroOneFiveCentralMember
     
Land 425us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightNineZeroAirportHighwaySevenZeroOneFiveCentralMember
     
Building and improvements 1,407us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightNineZeroAirportHighwaySevenZeroOneFiveCentralMember
     
Total 1,832us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightNineZeroAirportHighwaySevenZeroOneFiveCentralMember
     
Accumulated depreciation 12/31/2012 947us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenEightNineZeroAirportHighwaySevenZeroOneFiveCentralMember
     
600 Creek Road [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Delanco, NJ      
Initial Cost of Land 2,125us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroZeroCreekRoadMember
     
Building and Improvements 6,504us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroZeroCreekRoadMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (3,821)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroZeroCreekRoadMember
     
Land 1,557us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroZeroCreekRoadMember
     
Building and improvements 3,251us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroZeroCreekRoadMember
     
Total 4,808us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroZeroCreekRoadMember
     
Accumulated depreciation 12/31/2012 746us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixZeroZeroCreekRoadMember
     
6301 Hazeltine National Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Orlando, FL      
Initial Cost of Land 909us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroOneHazeltineNationalDriveMember
     
Building and Improvements 4,613us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroOneHazeltineNationalDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 57us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroOneHazeltineNationalDriveMember
     
Land 920us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroOneHazeltineNationalDriveMember
     
Building and improvements 4,659us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroOneHazeltineNationalDriveMember
     
Total 5,579us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroOneHazeltineNationalDriveMember
     
Accumulated depreciation 12/31/2012 1,718us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixThreeZeroOneHazeltineNationalDriveMember
     
12626 Silicon Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) San Antonio, TX      
Initial Cost of Land 768us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixTwoSixSiliconDriveMember
     
Building and Improvements 3,448us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixTwoSixSiliconDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (449)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixTwoSixSiliconDriveMember
     
Land 779us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixTwoSixSiliconDriveMember
     
Building and improvements 2,988us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixTwoSixSiliconDriveMember
     
Total 3,767us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixTwoSixSiliconDriveMember
     
Accumulated depreciation 12/31/2012 934us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneTwoSixTwoSixSiliconDriveMember
     
3100 Pinson Valley Parkway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Birmingham, AL      
Initial Cost of Land 303us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandOneHundredPinsonValleyParkwayMember
     
Building and Improvements 742us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandOneHundredPinsonValleyParkwayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (280)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandOneHundredPinsonValleyParkwayMember
     
Land 225us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandOneHundredPinsonValleyParkwayMember
     
Building and improvements 540us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandOneHundredPinsonValleyParkwayMember
     
Total 765us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandOneHundredPinsonValleyParkwayMember
     
Accumulated depreciation 12/31/2012 212us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandOneHundredPinsonValleyParkwayMember
     
3730 Wheeler Avenue [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Fort Smith, AR      
Initial Cost of Land 720us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenThreeZeroWheelerAvenueMember
     
Building and Improvements 2,800us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenThreeZeroWheelerAvenueMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (589)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenThreeZeroWheelerAvenueMember
     
Land 583us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenThreeZeroWheelerAvenueMember
     
Building and improvements 2,348us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenThreeZeroWheelerAvenueMember
     
Total 2,931us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenThreeZeroWheelerAvenueMember
     
Accumulated depreciation 12/31/2012 827us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeSevenThreeZeroWheelerAvenueMember
     
3200 Pond Station [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Jefferson County, KY      
Initial Cost of Land 2,074us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredPondStationMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 9,896us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredPondStationMember
     
Land 2,120us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredPondStationMember
     
Building and improvements 9,850us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredPondStationMember
     
Total 11,970us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredPondStationMember
     
Accumulated depreciation 12/31/2012 2,052us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeThousandTwoHundredPondStationMember
     
7501 NW 106th Terrace [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Kansas City, MO      
Encumbrances 10,997us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroOneNwOneZeroSixthTerraceMember
     
Initial Cost of Land 4,152us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroOneNwOneZeroSixthTerraceMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 13,659us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroOneNwOneZeroSixthTerraceMember
     
Land 4,228us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroOneNwOneZeroSixthTerraceMember
     
Building and improvements 13,583us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroOneNwOneZeroSixthTerraceMember
     
Total 17,811us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroOneNwOneZeroSixthTerraceMember
     
Accumulated depreciation 12/31/2012 2,108us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFiveZeroOneNwOneZeroSixthTerraceMember
     
600 Greene Drive [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Greenville, KY      
Initial Cost of Land 294us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixHundredGreeneDriveMember
     
Building and Improvements 8,570us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixHundredGreeneDriveMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision (727)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixHundredGreeneDriveMember
     
Land 296us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixHundredGreeneDriveMember
     
Building and improvements 7,841us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixHundredGreeneDriveMember
     
Total 8,137us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixHundredGreeneDriveMember
     
Accumulated depreciation 12/31/2012 4,094us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SixHundredGreeneDriveMember
     
Developments / Land Parcels [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Initial Cost of Land 159,831us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_RedevelopmentsDevelopementsDevelopableLandMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 5,930us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_RedevelopmentsDevelopementsDevelopableLandMember
     
Land 150,135us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_RedevelopmentsDevelopementsDevelopableLandMember
     
Building and improvements 15,626us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_RedevelopmentsDevelopementsDevelopableLandMember
     
Total 165,761us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_RedevelopmentsDevelopementsDevelopableLandMember
     
Accumulated depreciation 12/31/2012 2,184us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_RedevelopmentsDevelopementsDevelopableLandMember
     
Seven Four Five One Seven Four Seven Seven Airport Freeway [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Encumbrances 1,363us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Initial Cost of Land 256us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Building and Improvements 1,453us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 499us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Land 259us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Building and improvements 1,949us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Total 2,208us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Accumulated depreciation 12/31/2012 625us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneSevenFourSevenSevenAirportFreewayMember
     
Seven Four Five Zero Whitehall Street [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 104us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroWhitehallStreetMember
     
Building and Improvements 591us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroWhitehallStreetMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 339us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroWhitehallStreetMember
     
Land 105us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroWhitehallStreetMember
     
Building and improvements 929us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroWhitehallStreetMember
     
Total 1,034us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroWhitehallStreetMember
     
Accumulated depreciation 12/31/2012 250us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveZeroWhitehallStreetMember
     
Three Zero Zero Zero Wesley Way [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Initial Cost of Land 208us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWesleyWayMember
     
Building and Improvements 1,181us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWesleyWayMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 18us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWesleyWayMember
     
Land 211us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWesleyWayMember
     
Building and improvements 1,196us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWesleyWayMember
     
Total 1,407us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWesleyWayMember
     
Accumulated depreciation 12/31/2012 367us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_ThreeZeroZeroZeroWesleyWayMember
     
Seven Four Five One Dogwood Park [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Richland Hills, TX      
Encumbrances 666us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
Initial Cost of Land 133us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
Building and Improvements 753us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 184us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
Land 134us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
Building and improvements 936us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
Total 1,070us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
Accumulated depreciation 12/31/2012 258us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_SevenFourFiveOneDogwoodParkMember
     
One Zero One Three Three One Avenue M [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Prairie, TX      
Initial Cost of Land 300us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneThreeThreeOneAvenueMMember
     
Building and Improvements 1,504us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneThreeThreeOneAvenueMMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 240us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneThreeThreeOneAvenueMMember
     
Land 302us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneThreeThreeOneAvenueMMember
     
Building and improvements 1,742us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneThreeThreeOneAvenueMMember
     
Total 2,044us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneThreeThreeOneAvenueMMember
     
Accumulated depreciation 12/31/2012 573us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneZeroOneThreeThreeOneAvenueMMember
     
One One Seven Two Eight Four One One Three Th Street D [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Grand Prairie, TX      
Encumbrances 1,933us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Initial Cost of Land 700us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Building and Improvements 3,509us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 5us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Land 704us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Building and improvements 3,510us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Total 4,214us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Accumulated depreciation 12/31/2012 1,239us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_OneOneSevenTwoEightFourOneOneThreeThStreetDMember
     
Five Eight One Welltown Road Tyson Blvd [Member]        
Real Estate and Accumulated Depreciation [Line Items]        
Location (City/State) Winchester, VA      
Initial Cost of Land 2,320us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightOneWelltownRoadTysonBlvdMember
     
Costs capitalized subsequent to acquisition or completion and valuation provision 10,945us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightOneWelltownRoadTysonBlvdMember
     
Land 2,401us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightOneWelltownRoadTysonBlvdMember
     
Building and improvements 10,864us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightOneWelltownRoadTysonBlvdMember
     
Total 13,265us-gaap_RealEstateGrossAtCarryingValue
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightOneWelltownRoadTysonBlvdMember
     
Accumulated depreciation 12/31/2012 $ 2,054us-gaap_RealEstateAccumulatedDepreciation
/ us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis
= fr_FiveEightOneWelltownRoadTysonBlvdMember