Investments in Partially Owned Entities (Schedule of Income (Loss)) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	May 19, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Schedule Of Equity Method Investments
Equity in net income				$ 72,207	$ 83,775
Distributions of income from partially owned entities				131,308	137,758
Our share of net income (loss)		$ 18,269	$ 24,341	$ 72,207	83,775
Fifth Avenue and Times Square JV
Schedule Of Equity Method Investments
Equity method ownership percentage		51.50%		51.50%
Equity in net income		$ 10,917	11,941	$ 27,057	41,915
Distributions of income from partially owned entities		9,430	9,430	27,985	27,985
Our share of net income (loss)		$ 20,347	21,371	55,042	69,900
Default accrual interest amount				$ 5,120
Alexander's
Schedule Of Equity Method Investments
Equity method ownership percentage		32.40%		32.40%
Equity in net income		$ 3,341	4,740	$ 10,230	14,235
Management, leasing and development fees		1,184	1,170	4,056	3,352
Net gain on sale of land	$ 16,396	0	0	16,396	0
Our share of net income (loss)		4,525	5,910	30,682	17,587
Partially owned office buildings/land
Schedule Of Equity Method Investments
Our share of net income (loss)		(7,647)	(5,286)	(16,864)	(8,974)
Other investments
Schedule Of Equity Method Investments
Our share of net income (loss)		$ 1,044	$ 2,346	$ 3,347	$ 5,262