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Investments in Unconsolidated Joint Ventures - Acquisition, Development and Construction Arrangements/Sale of Joint Venture Interest or Property (Details) $ in Thousands | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2019 USD ($) note | May 31, 2019 USD ($) | Jan. 31, 2019 USD ($) | Nov. 30, 2018 USD ($) | Jul. 31, 2018 USD ($) | Jun. 30, 2018 USD ($) | May 31, 2018 USD ($) | Apr. 30, 2018 USD ($) | Feb. 28, 2018 USD ($) | Sep. 30, 2017 USD ($) | May 31, 2017 USD ($) | Dec. 31, 2019 USD ($) note | Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Mar. 31, 2019 USD ($) | Dec. 31, 2018 USD ($) | Sep. 30, 2018 USD ($) | Jun. 30, 2018 USD ($) | Mar. 31, 2018 USD ($) | Dec. 31, 2019 USD ($) note | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Aug. 31, 2018 USD ($) | Apr. 30, 2017 USD ($)
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | $ 2,912,842 |  |  |  |  |  |  |  |  |  |  | $ 2,912,842 |  |  |  | $ 3,019,020 |  |  |  | $ 2,912,842 | $ 3,019,020 |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  |  |  |  | 0 | $ 0 | $ 59,015 | $ 17,166 | 167,445 | $ 70,937 | $ 72,025 | $ (6,440) | 76,181 | 303,967 | $ 16,166 |  |
Employee-related liabilities | 4,000 |  |  |  |  |  |  |  |  |  |  | 4,000 |  |  |  | 11,700 |  |  |  | 4,000 | 11,700 | 0 |  |
(Loss) gain on sale of real estate, net |  |  |  |  |  |  |  |  |  |  |  | (19,241) | $ 3,541 | $ 0 | $ (1,049) | (36,984) | $ (2,504) | $ (14,790) | $ 23,521 | (16,749) | (30,757) | 73,241 |  |
Madison Avenue 747 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
(Loss) gain on sale of real estate, net |  |  |  |  |  |  |  |  |  |  | $ 13,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Participating Financing Due February 2022 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | 0 |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  | 44,357 |  |  |  | 0 | 44,357 |  |  |
Mezzanine Loans And Preferred Equity |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Acquisition, development and construction arrangements, carrying value | $ 0 |  |  |  |  |  |  |  |  |  |  | $ 0 |  |  |  | 44,357 |  |  |  | $ 0 | 44,357 |  |  |
1515 Broadway |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,950,000 |  |
102 Greene Street |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 43,500
Employee-related liabilities |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 900
76 11th Avenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of notes owned | note | 2 |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  | 2 |  |  |  |
Joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in unconsolidated joint ventures | $ 2,912,842 |  |  |  |  |  |  |  |  |  |  | $ 2,912,842 |  |  |  |  |  |  |  | $ 2,912,842 |  |  |  |
Joint venture | East 21 Street 66 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation | 2,900 |  |  |  |  |  |  |  |  |  |  | 2,900 |  |  |  |  |  |  |  | 2,900 |  |  |  |
Gain (Loss) on Sale | 279 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | Fifth Avenue, 521 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  | 50.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  | $ 381,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  | $ 57,874 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | Spring Street 131 to 137 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  | 20.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  | $ 216,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  | $ 17,660 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | Stonehenge Portfolio |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation | $ 468,800 |  |  |  |  |  |  |  |  |  |  | $ 468,800 |  |  |  | $ 331,100 |  |  |  | 468,800 | 331,100 | 300,000 |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ (2,408) | $ (6,063) | $ 871 |  |
Joint venture | 3 Columbus Circle |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  | 48.90% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  | $ 851,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  | $ 160,368 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | Mezzanine Loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 33.33% |
Gross asset valuation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 15,000 |
Joint venture | 724 Fifth Avenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  | 49.90% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  | $ 365,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  | $ 64,587 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | Jericho Plaza |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  |  | 11.67% |  |  |  |  |  |  |  |  |  |  |  | 11.67% |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  | $ 117,400 |  |  |  |  |  |  |  |  |  |  |  | $ 117,400 |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  | $ 147 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | 1745 Broadway |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  |  |  | 56.87% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  |  | $ 633,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  | $ 52,038 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | 175-225 Third Street Brooklyn, New York |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  |  |  |  | 95.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  |  |  | $ 115,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  | $ 19,483 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | 1515 Broadway |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  |  |  |  |  | 13.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  |  |  |  | $ 1,950,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  | $ 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | 102 Greene Street |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  |  |  |  |  | $ 43,500 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain (Loss) on Sale |  |  |  |  |  |  |  |  |  | $ 283 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Joint venture | 76 11th Avenue |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Ownership Interest Sold |  |  |  |  |  |  |  |  |  |  | 33.33% |  |  |  |  |  |  |  |  |  |  |  |  |
Gross asset valuation |  |  |  |  |  |  |  |  |  |  | $ 138,240 |  |  |  |  |  |  |  |  |  |  |  |  |

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