Related Party Transactions (Fees to Vornado) (Details) - Vornado - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Summary of fees to Vornado
Fees to related party	$ 8,616	$ 12,630	$ 7,039
Company management fees
Summary of fees to Vornado
Fees to related party	2,800	2,800	2,800
Development fees
Summary of fees to Vornado
Fees to related party	489	29	125
Leasing fees
Summary of fees to Vornado
Fees to related party	276	4,786	13
Property management, cleaning, engineering and security services
Summary of fees to Vornado
Fees to related party	$ 5,051	$ 5,015	$ 4,101