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Investment in Real Estate Investment in Real Estate - Summary of Industrial Property Acquisitions (Details) $ in Thousands, ft² in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($) ft² Property | Dec. 31, 2019 USD ($) ft² Property | Dec. 31, 2018 USD ($) ft² Property
Real Estate Properties [Line Items] |  |  |
Number of industrial properties | Property | 427 |  |
Gross leasable area (GLA) of industrial properties | ft² | 62.8 |  |
Acquisition Activity |  |  |
Real Estate Properties [Line Items] |  |  |
Number of industrial properties | Property | 8 | 9 | 10
Gross leasable area (GLA) of industrial properties | ft² | 1.5 | 0.5 | 1.0
Purchase price of industrial properties acquired | $ | $ 224,027 | $ 147,887 | $ 167,546
Purchase price of land parcels acquired | $ | $ 69,617 | $ 81,082 | $ 38,976

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- Definition The amount of assets acquired. + References No definition available. + Details
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Balance Type: | debit
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- Definition Purchase Price of Land + References No definition available. + Details
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Namespace Prefix: | fr_
Data Type: | xbrli:monetaryItemType
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- Definition Area of a real estate property. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:areaItemType
Balance Type: | na
Period Type: | instant

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- Definition The number of real estate properties owned as of the balance sheet date. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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