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Summary of Significant Accounting Policies - Deferred Leasing Intangibles Included in Total Assets (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization,Total Assets	$ 36,327	$ 34,869

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- Definition

Accumulated Amortization Of Intangible Lease Assets

+ References

No definition available.

+ Details

Name:	fr_AccumulatedAmortizationOfIntangibleLeaseAssets
Namespace Prefix:	fr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration