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Accumulated Other Comprehensive Loss - Additional Information (Details) $ in Thousands | 3 Months Ended
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Mar. 31, 2018 USD ($)
Accumulated Other Comprehensive Loss [Abstract] |
Amortization to be reclassified from OCI into income | $ 95

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- Definition Accumulated Other Comprehensive Loss [Abstract] + References No definition available. + Details
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Namespace Prefix: | fr_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition The estimated value of gains (losses), net anticipated to be transferred in the future from accumulated other comprehensive income into earnings. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
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