Investments in Partially Owned Entities (Summary of Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
640 Fifth Avenue
Schedule of Equity Method Investments [Line Items]
Mortgage loans on real estate, face amount of mortgages	$ 500,000
7 West 34th Street
Schedule of Equity Method Investments [Line Items]
Mortgage loans on real estate, face amount of mortgages	300,000
Partially Owned Properties
Schedule of Equity Method Investments [Line Items]
Equity method investment pro rata share debt of partially owned entities	$ 2,697,226	$ 2,699,405
Partially Owned Office Buildings/Land
Schedule of Equity Method Investments [Line Items]
Debt instrument, interest rate, effective percentage	4.82%
Equity method investment debt of partially owned entities	$ 3,288,977	3,297,999
Alexander's
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	32.40%
Debt instrument, interest rate, effective percentage	4.12%
Equity method investment debt of partially owned entities	$ 1,096,544	1,096,544
Fifth Avenue and Times Square JV
Schedule of Equity Method Investments [Line Items]
Equity method ownership percentage	51.50%
Debt instrument, interest rate, effective percentage	5.55%
Equity method investment debt of partially owned entities	$ 921,000	950,000
Other equity method investments
Schedule of Equity Method Investments [Line Items]
Debt instrument, interest rate, effective percentage	5.14%
Equity method investment debt of partially owned entities	$ 1,377,492	$ 1,342,162