Investments in Partially Owned Entities (Summary of Investments) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ 3,270,229	$ 3,297,389
Other liabilities
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ (79,464)	(78,985)
Fifth Avenue and Times Square JV
Schedule Of Equity Method Investments
Equity method ownership percentage	51.50%
Carrying amount of investments in partially owned entities	$ 2,771,041	2,770,633
Partially owned office buildings/land
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ 282,057	306,989
Alexanders Inc
Schedule Of Equity Method Investments
Equity method ownership percentage	32.40%
Carrying amount of investments in partially owned entities	$ 91,544	91,405
Other investments
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ 125,587	128,362
7 West 34th Street
Schedule Of Equity Method Investments
Equity method ownership percentage	53.00%
7 West 34th Street | Other liabilities
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ (63,394)	(60,918)
85 Tenth Avenue
Schedule Of Equity Method Investments
Equity method ownership percentage	49.90%
85 Tenth Avenue | Other liabilities
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ (16,070)	$ (18,067)