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Derivatives - Fair Value Measurements on Recurring Basis (Detail) (Series F Agreement [Member], USD $) In Thousands, unless otherwise specified | Sep. 30, 2013 | Dec. 31, 2012
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Fair Value On Recurring Basis [Line Items] |  |
Fair Value of Liabilities | $ 0 | $ (826)
Fair Value, Measurements, Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) |  |
Fair Value On Recurring Basis [Line Items] |  |
Fair Value of Liabilities | 0 | 0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) |  |
Fair Value On Recurring Basis [Line Items] |  |
Fair Value of Liabilities | 0 | 0
Fair Value, Measurements, Recurring [Member] | Unobservable Inputs (Level 3) |  |
Fair Value On Recurring Basis [Line Items] |  |
Fair Value of Liabilities | $ 0 | $ (826)

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

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- Definition This element represents the aggregate of the liabilities reported on the balance sheet at period end measured at fair value by the entity. This element is intended to be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258 + Details
Name: | us-gaap_LiabilitiesFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant