Investments in Partially Owned Entities (Alexander's Inc.) (Details) - Alexander's - USD ($) $ / shares in Units, $ in Thousands	Aug. 01, 2025	Sep. 30, 2025
Schedule Of Equity Method Investments
Equity method ownership percentage (as percent)		32.40%
Mortgages Payable | Alexander's
Schedule Of Equity Method Investments
Extension term	60 days
Debt amount	$ 300,000
Equity Method Investee
Schedule Of Equity Method Investments
Ownership common shares, investee (in shares)		1,654,068
Equity method ownership percentage (as percent)		32.40%
Closing share price (in dollars per share)		$ 234.49
Equity method investment fair value		$ 387,862
Excess of investee's fair value over carrying amount		334,270
Excess of investee's carrying amount over equity in net assets		$ 29,071