Supplemental Information to Statements of Cash Flows - Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental Cash Flow Information [Line Items]
Interest Paid, Net of Interest Expense Capitalized in Connection with Development Activity	$ 65,436us-gaap_InterestPaidNet	$ 65,978us-gaap_InterestPaidNet	$ 77,795us-gaap_InterestPaidNet
Interest Expense Capitalized in Connection with Development Activity	1,248us-gaap_InterestPaidCapitalized	2,813us-gaap_InterestPaidCapitalized	1,768us-gaap_InterestPaidCapitalized
Income Taxes (Refunded) Paid	(105)us-gaap_IncomeTaxesPaidNet	5,433us-gaap_IncomeTaxesPaidNet	(295)us-gaap_IncomeTaxesPaidNet
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distributions Payable	11,949	10,289
Exchange of Limited Partnership Units for General Partnership Units:
Conversion of Limited Partner Units to General Partner Units	0	0	0
Assumption of Indebtedness and Other Liabilities in Connection with the Acquisition of Real Estate	339us-gaap_LiabilitiesAssumed1	483us-gaap_LiabilitiesAssumed1	12,026us-gaap_LiabilitiesAssumed1
Notes Receivable Issued in Conjunction with Certain Property Sales	0us-gaap_NotesIssued1	12,520us-gaap_NotesIssued1	0us-gaap_NotesIssued1
Accounts Payable Related to Construction in Progress and Additions to Investment in Real Estate	13,506	10,402	9,584
Write-off of Fully Depreciated Assets	(40,962)fr_WriteOffOfFullyDepreciatedAssets	(52,800)fr_WriteOffOfFullyDepreciatedAssets	(39,208)fr_WriteOffOfFullyDepreciatedAssets
General Partner Units
Exchange of Limited Partnership Units for General Partnership Units:
Conversion of Limited Partner Units to General Partner Units	2,155	996	4,763
Limited Partner Units
Exchange of Limited Partnership Units for General Partnership Units:
Conversion of Limited Partner Units to General Partner Units	(2,155)	(996)	(4,763)
General and Limited Partner Units
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distributions Payable	11,949	9,837	0
Preferred Units
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distributions Payable	$ 0	$ 452	$ 452

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The non-cash amount of fully depreciated assets being written off during the period.

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Future cash outflow to pay for purchases of fixed assets that have occurred.

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Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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The amount of cash paid during the current period for interest that is capitalized.

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The fair value of liabilities assumed in noncash investing or financing activities.

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Value of stock issued during the period upon the conversion of units. An example of a convertible unit is an umbrella partnership real estate investment trust unit (UPREIT unit).

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