Investments in Partially Owned Entities (Schedule of Income (Loss) ) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($) investment	Dec. 31, 2021 USD ($)
Schedule of Equity Method Investments [Line Items]
Equity in net income	$ 38,689	$ (461,351)	$ 130,517
Return on preferred equity, net of our share of the expense	172,873	184,501	214,521
Non-cash impairment loss	(45,007)	(19,098)	(7,880)
Our share of net income (loss)	38,689	(461,351)	130,517
Net gains on disposition of wholly owned and partially owned assets	$ 71,199	100,625	50,770
Fifth Avenue and Times Square JV
Schedule of Equity Method Investments [Line Items]
Ownership interest	51.50%
Equity in net income	$ 35,209	55,248	47,144
Return on preferred equity, net of our share of the expense	37,416	37,416	37,416
Non-cash impairment loss	0	(489,859)	0
Our share of net income (loss)	72,625	(397,195)	84,560
Default accrual interest amount	$ 5,120
Alexander's
Schedule of Equity Method Investments [Line Items]
Ownership interest	32.40%
Equity in net income	$ 15,441	18,439	20,116
Management, leasing and development fees	5,238	4,534	5,429
Net realized (loss) income on exited investments	16,396	0	14,576
Our share of net income (loss)	37,075	22,973	40,121
Partially Owned Office Buildings/Land
Schedule of Equity Method Investments [Line Items]
Our share of net income (loss)	(73,589)	(110,261)	6,384
Other investments
Schedule of Equity Method Investments [Line Items]
Our share of net income (loss)	2,578	23,132	$ (548)
Net gains on disposition of wholly owned and partially owned assets		$ 17,185
Number of investments | investment		2
650 Madison Avenue
Schedule of Equity Method Investments [Line Items]
Non-cash impairment loss	$ (50,458)	$ (93,353)