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Commitments and Contingencies (Details Textual) (USD $) In Thousands, unless otherwise specified | 12 Months Ended | 3 Months Ended
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Dec. 31, 2011 Property | Dec. 31, 2010 | Dec. 31, 2009 | Dec. 31, 2011 Minimum [Member] | Dec. 31, 2011 Maximum [Member]
Additional Commitments and Contingencies (Textual) [Abstract] |  |  |  |  |
Expiry date of letter of credit |  |  |  | Febuary 2012 | July 2013
Commitments and Contingencies (Textual) [Abstract] |  |  |  |  |
Number leased properties having the options to purchase the property | 12 |  |  |  |
Letters of credit outstanding in aggregate amount | $ 6,780 |  |  |  |
Operating and ground lease expense | $ 1,955 | $ 3,047 | $ 4,181 |  |

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- Details
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Namespace Prefix: | fr_
Data Type: | xbrli:stringItemType
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- Details
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- Definition Reflects when the letter of credits terminate, which may be presented in a variety of ways (year, month and year, day, month and year, quarter). + References No definition available. + Details
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Namespace Prefix: | fr_
Data Type: | us-types:dateStringItemType
Balance Type: | na
Period Type: | duration

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- Definition The number of operating leases which contain options to purchase the property. + References No definition available. + Details
Name: | fr_NumberOfLeasesWithOptionsToPurchaseProperties
Namespace Prefix: | fr_
Data Type: | xbrli:integerItemType
Balance Type: | na
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- Definition The total amount of the contingent obligation under letters of credit outstanding as of the reporting date. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717 + Details
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