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Area of a real estate property.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Investments in Unconsolidated Joint Ventures - Additional Information (Details) $ in Thousands	1 Months Ended		3 Months Ended		12 Months Ended
	Apr. 30, 2021 USD ($)	Oct. 31, 2016	Mar. 31, 2021 USD ($) ft² unit partner	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
General information on each joint venture
Equity method investments \| $			$ 3,698,701		$ 3,823,322
Net equity investment in VIEs in which the entity is not primary beneficiary \| $			$ 132,700		$ 134,000
Unaudited Approximate Square Feet (sqft)			29,134,784
(Loss) gain on sale of real estate, net \| $			$ (1,388)	$ 72,636
One Madison Avenue
General information on each joint venture
Ownership percentage deconsolidated					50.50%
Investment fair value adjustment \| $			$ 2,700		$ 187,500
Stonehenge Portfolio
General information on each joint venture
Ownership Interest Disposed		90.00%
East 400 Street 57
General information on each joint venture
Ownership Interest Disposed		51.00%
One Madison Avenue
General information on each joint venture
Investment in joint venture aggregate equity committed by partner \| $					$ 492,200
Investment in joint venture aggregate maximum ownership percentage					49.50%
Investment in joint venture, number of partners \| partner			2
Investment in joint venture, ownership percentage			9.00%
East 400 Street 57
General information on each joint venture
Ownership percentage in disposed asset		49.00%
East 400 Street 57 \| Subsequent Event
General information on each joint venture
Asset impairment charges \| $	$ 5,700
21 East 66th Street \| Three Retail and Two Residential Units
General information on each joint venture
Ownership Interest Disposed			32.28%
Number of stores \| unit			3
Number of residential units \| unit			1
21 East 66th Street \| Three Residential Units
General information on each joint venture
Ownership Interest Disposed			16.14%
Number of residential units \| unit			3
Joint venture
General information on each joint venture
Equity method investments \| $			$ 3,698,701
Equity method investments with negative book value \| $			$ 92,400
Joint venture \| 100 Park Avenue
General information on each joint venture
Ownership Interest Disposed			49.90%
Economic Interest (as a percent)			49.90%
Unaudited Approximate Square Feet (sqft)			834,000
Joint venture \| 717 Fifth Avenue
General information on each joint venture
Ownership Interest Disposed			10.92%
Economic Interest (as a percent)			10.92%
Unaudited Approximate Square Feet (sqft)			119,500
Joint venture \| 800 Third Avenue
General information on each joint venture
Ownership Interest Disposed			60.52%
Economic Interest (as a percent)			60.52%
Unaudited Approximate Square Feet (sqft)			526,000
Interest rate, fixed rate debt (as a percent)			3.37%
Joint venture \| 919 Third Avenue
General information on each joint venture
Ownership Interest Disposed			51.00%
Economic Interest (as a percent)			51.00%
Unaudited Approximate Square Feet (sqft)			1,454,000
Interest rate, fixed rate debt (as a percent)			5.12%
Joint venture \| 11 West 34th Street
General information on each joint venture
Ownership Interest Disposed			30.00%
Economic Interest (as a percent)			30.00%
Unaudited Approximate Square Feet (sqft)			17,150
Joint venture \| 280 Park Avenue
General information on each joint venture
Ownership Interest Disposed			50.00%
Economic Interest (as a percent)			50.00%
Unaudited Approximate Square Feet (sqft)			1,219,158
Joint venture \| 1552-1560 Broadway
General information on each joint venture
Ownership Interest Disposed			50.00%
Economic Interest (as a percent)			50.00%
Unaudited Approximate Square Feet (sqft)			57,718
Joint venture \| 10 East 53rd Street
General information on each joint venture
Ownership Interest Disposed			55.00%
Economic Interest (as a percent)			55.00%
Unaudited Approximate Square Feet (sqft)			354,300
Joint venture \| 21 East 66th Street
General information on each joint venture
Ownership Interest Disposed			32.28%
Economic Interest (as a percent)			32.28%
Unaudited Approximate Square Feet (sqft)			13,069
Interest rate, fixed rate debt (as a percent)			3.60%
Joint venture \| 650 Fifth Avenue
General information on each joint venture
Ownership Interest Disposed			50.00%
Economic Interest (as a percent)			50.00%
Unaudited Approximate Square Feet (sqft)			69,214
Joint venture \| 121 Greene Street
General information on each joint venture
Ownership Interest Disposed			50.00%
Economic Interest (as a percent)			50.00%
Unaudited Approximate Square Feet (sqft)			7,131
Joint venture \| Stonehenge Portfolio
General information on each joint venture
Ownership Interest Disposed		10.00%
Unaudited Approximate Square Feet (sqft)			1,439,016
Interest rate, fixed rate debt (as a percent)			3.50%
Joint venture \| 605 West 42nd Street
General information on each joint venture
Ownership Interest Disposed			20.00%
Economic Interest (as a percent)			20.00%
Unaudited Approximate Square Feet (sqft)			927,358
Joint venture \| 11 Madison Avenue
General information on each joint venture
Ownership Interest Disposed			60.00%
Economic Interest (as a percent)			60.00%
Unaudited Approximate Square Feet (sqft)			2,314,000
Interest rate, fixed rate debt (as a percent)			3.84%
Joint venture \| East 400 Street 57
General information on each joint venture
Ownership Interest Disposed			51.00%
Economic Interest (as a percent)			41.00%
Unaudited Approximate Square Feet (sqft)			290,482
Interest rate, fixed rate debt (as a percent)			3.00%
Joint venture \| One Vanderbilt
General information on each joint venture
Ownership Interest Disposed			71.01%
Economic Interest (as a percent)			71.01%
Unaudited Approximate Square Feet (sqft)			1,657,198
Joint venture \| Worldwide Plaza
General information on each joint venture
Ownership Interest Disposed			24.35%
Economic Interest (as a percent)			24.35%
Unaudited Approximate Square Feet (sqft)			2,048,725
Interest rate, fixed rate debt (as a percent)			3.98%
Joint venture \| 1515 Broadway
General information on each joint venture
Ownership Interest Disposed			56.87%
Economic Interest (as a percent)			56.87%
Unaudited Approximate Square Feet (sqft)			1,750,000
Interest rate, fixed rate debt (as a percent)			3.93%
Joint venture \| 2 Herald Square
General information on each joint venture
Ownership Interest Disposed			51.00%
Economic Interest (as a percent)			51.00%
Unaudited Approximate Square Feet (sqft)			369,000
Joint venture \| 115 Spring Street
General information on each joint venture
Ownership Interest Disposed			51.00%
Economic Interest (as a percent)			51.00%
Unaudited Approximate Square Feet (sqft)			5,218
Joint venture \| 15 Beekman
General information on each joint venture
Ownership Interest Disposed			20.00%
Economic Interest (as a percent)			20.00%
Unaudited Approximate Square Feet (sqft)			221,884
Joint venture \| 85 Fifth Avenue
General information on each joint venture
Ownership Interest Disposed			36.30%
Economic Interest (as a percent)			36.30%
Unaudited Approximate Square Feet (sqft)			12,946
Joint venture \| One Madison Avenue
General information on each joint venture
Ownership Interest Disposed			50.50%
Economic Interest (as a percent)			50.50%
Unaudited Approximate Square Feet (sqft)			1,048,700