Investments in Partially Owned Entities (Fifth Avenue and Times Square JV) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Real estate held-for-sale		$ 128,215	$ 408,918
Net gain on transfer to Fifth Avenue and Times Square JV		0	2,571,099	$ 0
Non-cash impairment loss		(236,286)	(8,065)	(12,000)
Majority-Owned Subsidiary, Unconsolidated | Property Management Fee
Schedule of Equity Method Investments [Line Items]
Revenue from related parties		$ 3,982	3,085
Fifth Avenue and Times Square JV
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage		51.50%
Real estate held-for-sale	$ 5,556,000
Net gain on transfer to Fifth Avenue and Times Square JV	2,571,000
Net gain from real estate investment partnership, attributable to noncontrolling interest	$ 11,945
Non-cash impairment loss		$ (413,349)	0	$ 0
Non-cash impairment loss related to noncontrolling interest		4,289
Basis difference in carrying amount		$ 403,029
Property management fee agreement percentage of income		2.00%
Development fee percent		5.00%
Supervisory fee, percent		1.50%
Fifth Avenue and Times Square JV | Building Maintenance Service
Schedule of Equity Method Investments [Line Items]
Fee income recognized by equity method investees for building maintenance services		$ 3,595	$ 3,087
Fifth Avenue and Times Square JV | Joint Venture
Schedule of Equity Method Investments [Line Items]
Aggregate of preferred equity interests		$ 1,828,000
Fifth Avenue and Times Square JV | Joint Venture | Investors
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	48.50%	48.50%
Equity method investment, effective ownership percentage		47.20%
Fifth Avenue and Times Square JV | Joint Venture | Percentage For First Five Years
Schedule of Equity Method Investments [Line Items]
Debt instrument, interest rate, stated percentage		4.25%
Fifth Avenue and Times Square JV | Joint Venture | Increase in Percentage After Fifth Anniversary
Schedule of Equity Method Investments [Line Items]
Debt instrument, interest rate, stated percentage		4.75%
Fifth Avenue and Times Square JV | Vornado Realty Trust
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage		51.50%
Equity method investment, effective ownership percentage		51.00%