Investments in Partially Owned Entities (Alexander's Inc.) (Details) - Alexander's - USD ($) $ / shares in Units, $ 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
Ownership common shares, investee (in shares)		1,654,068		1,654,068
Equity method ownership percentage		32.40%		32.40%
Equity method investment, agreement to sell, amount	$ 71,060
Net realized gain (loss) on exited investments	16,396	$ 0	$ 0	$ 16,396	$ 0
Proceeds from commissions received	711
Commissions paid to third-party broker	$ 250
Closing share price (in dollars per share)		$ 182.23		$ 182.23
Equity method investment fair value		$ 301,421		$ 301,421
Excess of investee's fair value over carrying amount		209,507		209,507
Excess of investee's carrying amount over equity in net assets		$ 29,551		$ 29,551