Investments in Unconsolidated Joint Ventures - Acquisition, Development and Construction Arrangements/Sale of Joint Venture Interest or Property (Details) $ in Thousands	1 Months Ended								12 Months Ended
	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Apr. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) retailAsset	May 31, 2019 USD ($)	Jan. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) retailAsset
Schedule of Equity Method Investments [Line Items]
Gain (Loss) on Sale									$ (32,757)	$ 2,961	$ 76,181
Employee-related liabilities					$ 0	$ 4,000			$ 1,400	$ 0	$ 4,000
400 East 57th Street
Schedule of Equity Method Investments [Line Items]
Asset impairment loss			$ 5,700
21 East 66th Street
Schedule of Equity Method Investments [Line Items]
Number of residential units sold | retailAsset						1					1
Joint venture | 400 East 57th Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest Sold	41.00%
Gross asset valuation	$ 133,500
Gain (Loss) on Sale	$ (1,000)
Joint venture | 605 West 42nd Street - Sky
Schedule of Equity Method Investments [Line Items]
Ownership Interest Sold		20.00%
Gross asset valuation		$ 858,100
Gain (Loss) on Sale		$ 8,900
Joint venture | 55 West 46th Street - Tower 46
Schedule of Equity Method Investments [Line Items]
Ownership Interest Sold				25.00%
Gross asset valuation				$ 275,000
Gain (Loss) on Sale				$ (15,200)
Joint venture | 333 East 22nd Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest Sold					33.33%					33.33%
Gross asset valuation					$ 1,600					$ 1,600
Gain (Loss) on Sale					$ 3,000
Joint venture | 21 East 66th Street
Schedule of Equity Method Investments [Line Items]
Gross asset valuation						$ 2,900					$ 2,900
Gain (Loss) on Sale						300
Joint venture | 521 Fifth Avenue
Schedule of Equity Method Investments [Line Items]
Ownership Interest Sold							50.50%
Gross asset valuation							$ 381,000
Gain (Loss) on Sale							$ 57,900
Joint venture | 131-137 Spring Street
Schedule of Equity Method Investments [Line Items]
Ownership Interest Sold								20.00%
Gross asset valuation								$ 216,000
Gain (Loss) on Sale								$ 17,700
Joint venture | Stonehenge Portfolio
Schedule of Equity Method Investments [Line Items]
Gross asset valuation						$ 468,800					468,800
Gain (Loss) on Sale											$ (2,400)