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Leases - Lessor Narrative (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Lessor, Lease, Description [Line Items] |  |  |
Revenues | $ 199,142 | $ 226,350 | $ 232,825
Minimum |  |  |
Lessor, Lease, Description [Line Items] |  |  |
Lessor, operating lease, term (years) | 5 years |  |
Maximum |  |  |
Lessor, Lease, Description [Line Items] |  |  |
Lessor, operating lease, term (years) | 25 years |  |
The Alexander apartment tower | Minimum |  |  |
Lessor, Lease, Description [Line Items] |  |  |
Lessor, operating lease, term (years) | 1 year |  |
The Alexander apartment tower | Maximum |  |  |
Lessor, Lease, Description [Line Items] |  |  |
Lessor, operating lease, term (years) | 2 years |  |
Revenue Benchmark | Bloomberg | Customer Concentration Risk |  |  |
Lessor, Lease, Description [Line Items] |  |  |
Revenues | $ 109,066 | $ 109,113 | $ 107,356
Percentage rent contributed by tenant | 55.00% | 48.00% | 46.00%

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