Investments in Partially Owned Entities (Schedule of Income (Loss)) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	May 19, 2023	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Schedule Of Equity Method Investments
Equity in net income				$ 53,938	$ 59,434
Our share of net income (loss)		$ 37,272	$ 25,720	$ 53,938	59,434
Fifth Avenue and Times Square JV
Schedule Of Equity Method Investments
Equity method ownership percentage		51.50%		51.50%
Equity in net income		$ 5,941	13,665	$ 16,140	29,974
Return on preferred equity, net of our share of the expense		9,329	9,329	18,555	18,555
Our share of net income (loss)		15,270	22,994	34,695	48,529
Default accrual interest amount		$ 5,120		$ 5,120
Alexander's
Schedule Of Equity Method Investments
Equity method ownership percentage		32.40%		32.40%
Net gain on sale of land	$ 16,396	$ 16,396	0	$ 16,396	0
Equity in net income		3,318	4,824	6,889	9,495
Management, leasing and development fees		1,699	1,162	2,872	2,182
Our share of net income (loss)		21,413	5,986	26,157	11,677
Partially owned office buildings/land
Schedule Of Equity Method Investments
Our share of net income (loss)		(254)	(4,980)	(9,217)	(3,688)
Other investments
Schedule Of Equity Method Investments
Our share of net income (loss)		$ 843	$ 1,720	$ 2,303	$ 2,916