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Earnings Per Share / Unit (EPS / EPU) - Additional Information (Detail) - shares | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
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Earnings Per Share [Abstract] |  |  |
Number Of Unvested Restricted Stock Awards Outstanding Included In Participating Securities | 387,947 | 463,774 | 488,861

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- Definition Number of unvested restricted stock awards outstanding included in participating securities. + References No definition available. + Details
Name: | fr_NumberOfUnvestedRestrictedStockAwardsOutstandingIncludedInParticipatingSecurities
Namespace Prefix: | fr_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
Name: | us-gaap_EarningsPerShareAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration