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v3.19.1

Segment Information - Real Estate Investments, at Cost of Company's Reportable Segments (Parenthetical) (Details) - a | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2019 | Dec. 31, 2018
Assets Held-for-sale [Member] | Land Held For Development [Member] |  |
Segment Reporting Information [Line Items] |  |
Acreage of Land |  | 37.9
3001-3003 and 3025 JFK Boulevard [Member] |  |
Segment Reporting Information [Line Items] |  |
Lease agreement term | 99 years | 99 years
Other [Member] | Assets Held-for-sale [Member] |  |
Segment Reporting Information [Line Items] |  |
Acreage of Land | 35.2 |
Other [Member] | Assets Held-for-sale [Member] | Land Held For Development [Member] |  |
Segment Reporting Information [Line Items] |  |
Acreage of Land | 35.2 | 35.2
Pennsylvania Suburbs [Member] | Assets Held-for-sale [Member] | Land Held For Development [Member] |  |
Segment Reporting Information [Line Items] |  |
Acreage of Land |  | 2.7

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