Investments in Partially Owned Entities (Summary of Investments) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ 3,299,629	$ 3,297,389
Other liabilities
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ (77,312)	(78,985)
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	$ (61,279)	(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	$ (16,033)	(18,067)
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	$ 2,773,505	2,770,633
Partially owned office buildings/land
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ 310,580	306,989
Alexanders Inc
Schedule Of Equity Method Investments
Equity method ownership percentage	32.40%
Carrying amount of investments in partially owned entities	$ 92,779	91,405
Other investments
Schedule Of Equity Method Investments
Carrying amount of investments in partially owned entities	$ 122,765	$ 128,362