Real Estate Fund Investments (Narrative) (Details) $ in Thousands			6 Months Ended
	Jun. 30, 2021 USD ($) investment	Dec. 31, 2020 USD ($) investment	Jun. 30, 2021 USD ($) investment	Apr. 12, 2021 USD ($)	Jun. 09, 2020 USD ($)
Investment Holdings
Aggregate fair value of Real Estate Fund investments (in US Dollars)	$ 3,739	$ 3,739	$ 3,739
Vornado Capital Partners Real Estate Fund
Investment Holdings
Equity method ownership percentage	25.00%		25.00%
Term of the Fund, years			8 years
Investment period for commitments of the Fund, years			3 years
Investment fund period expiration date			2013-07
Investment fund, extension of term			2023-02
Crowne Plaza Times Square Hotel Joint Venture
Investment Holdings
Default amount					$ 274,355
Debt instrument, interest rate, stated percentage (percent)	3.81%		3.81%
Debt instrument, default interest, percentage	3.00%		3.00%
Crowne Plaza Times Square Hotel Joint Venture | LIBOR
Investment Holdings
Spread over LIBOR (percent)			3.69%
Crowne Plaza Times Square Hotel Joint Venture | Joint Venture
Investment Holdings
Equity method ownership percentage	57.10%		57.10%
Crowne Plaza Times Square Hotel Joint Venture | Joint Venture | Crowne Plaza Time Square Hotel
Investment Holdings
Ownership percentage by noncontrolling owners	24.70%		24.70%
1100 Lincoln Road
Investment Holdings
Default amount				$ 82,750
Debt instrument, interest rate, stated percentage (percent)	4.65%		4.65%
Debt instrument, default interest, percentage	3.00%		3.00%
1100 Lincoln Road | Prime Rate
Investment Holdings
Spread over LIBOR (percent)			1.40%
Real estate fund investments
Investment Holdings
Number of investments held by fund (investment) | investment	4	4	4
Aggregate fair value of Real Estate Fund investments (in US Dollars)	$ 3,739	$ 3,739	$ 3,739
Fair value below cost	339,812		339,812
Unfunded commitments of fund	29,194		29,194
Real estate fund investments | Vornado Realty Trust
Investment Holdings
Unfunded commitments of fund	$ 9,266		$ 9,266