Supplemental Information to Statements of Cash Flows - Cash Flow Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Supplemental Cash Flow Information [Line Items]
Interest Expense Capitalized in Connection with Development Activity	$ 459us-gaap_InterestPaidCapitalized	$ 380us-gaap_InterestPaidCapitalized
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distribution Payable on Common Stock/Operating Partnership Units	14,912
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	0	0
Assumption of Liabilities in Connection with the Acquisition of Real Estate	0us-gaap_LiabilitiesAssumed1	138us-gaap_LiabilitiesAssumed1
Accounts Payable Related to Construction in Progress and Additions to Investment in Real Estate	8,881	12,650
Write-off of Fully Depreciated Assets	(9,849)fr_WriteOffOfFullyDepreciatedAssets	(9,863)fr_WriteOffOfFullyDepreciatedAssets
Noncontrolling Interest
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	(95)	(1,279)
Common Stock
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	0	1
Additional Paid-in- Capital
Exchange of Operating Partnership Units for Common Stock:
Conversion of Units to Common Stock	95	1,278
Common Stock/Operating Partnership Units
Supplemental Schedule of Non-Cash Investing and Financing Activities:
Distribution Payable on Common Stock/Operating Partnership Units	$ 14,912	$ 11,921

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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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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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