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Commitment and Contingencies - Future Minimum Rental Payments Under Terms of all Non-Cancelable Ground and Operating Leases (Parenthetical) (Detail) (USD $) | 12 Months Ended
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Dec. 31, 2012
Contractual Obligation Fiscal Year Maturity [Line Items] |
Minimum rental payments have not been reduced by minimum sublease rentals due in the future under non-cancelable subleases. | $ 8,339

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- Details
Name: | fr_ContractualObligationFiscalYearMaturityLineItems
Namespace Prefix: | fr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Operating Leases Future Minimum Sublease Income + References No definition available. + Details
Name: | fr_OperatingLeasesFutureMinimumSubleaseIncome
Namespace Prefix: | fr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration