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v3.10.0.1

Segment Information - Real Estate Investments, at Cost of Company's Reportable Segments (Parenthetical) (Details) | 9 Months Ended |
--- | --- | ---
Sep. 30, 2018 a property | Dec. 31, 2017 a
Segment Reporting Information [Line Items] |  |
Number of properties | property | 93 |
3025 and 3001-3003 JFK Boulevard [Member] |  |
Segment Reporting Information [Line Items] |  |
Lease agreement term | 99 years |
Assets Held-for-sale [Member] | Land Held For Development [Member] |  |
Segment Reporting Information [Line Items] |  |
Acreage of land | a | 37.9 |
Assets Held-for-sale [Member] | Pennsylvania Suburbs [Member] | Land Held For Development [Member] |  |
Segment Reporting Information [Line Items] |  |
Acreage of land | a | 2.7 |
Assets Held-for-sale [Member] | Other [Member] | Land Held For Development [Member] |  |
Segment Reporting Information [Line Items] |  |
Acreage of land | a | 35.2 | 13.1
Office Properties [Member] |  |
Segment Reporting Information [Line Items] |  |
Number of properties | property | 73 |
Office Properties [Member] | Assets Held-for-sale [Member] | Metropolitan DC [Member] |  |
Segment Reporting Information [Line Items] |  |
Number of properties | property | 8 |

X
- Definition Lease agreement term. + References No definition available. + Details
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- Definition Area of land held. + References No definition available. + Details
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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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- Details
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- Details
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- Details
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- Details
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- Details
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- Details
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