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Investments in Unconsolidated Joint Ventures Narrative (Details) $ in Thousands | Apr. 27, 2018 USD ($) ft² | Apr. 26, 2018 | Apr. 19, 2018 USD ($) ft² yr apartments | Jun. 30, 2018 USD ($) | Dec. 31, 2017 USD ($)
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Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Mortgage notes payable, net |  |  |  | $ 2,972,052 | $ 2,979,281
The Hub on Causeway - Residential [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership Percentage |  |  | 50.00% |  |
Construction Loan Facility Borrowing Capacity |  |  | $ 180,000 |  |
Debt Instrument, Basis Spread on Variable Rate |  |  | 2.00% |  |
Number of extensions |  |  | 2 |  |
Extension Option (in years) | yr |  |  | 1 |  |
Net Rentable Area (in sf) | ft² |  |  | 320,000 |  |
Number of apartment units | apartments |  |  | 440 |  |
540 Madison Avenue [Member] |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |
Ownership Percentage | 60.00% |  |  |  |
Mortgage notes payable, net | $ 120,000 |  |  |  |
Debt Instrument, Basis Spread on Variable Rate | 1.10% | 1.50% |  |  |
Net Rentable Area (in sf) | ft² | 284,000 |  |  |  |

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