Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Alexanders Inc
Related Party Transaction
Percentage of affiliated entity owned by company	32.40%
Percentage of affiliated entity owned by related parties	26.10%
Interstate Properties
Related Party Transaction
Percentage of company owned by related party	6.90%
Related party transaction annual fee percentage	4.00%
Term of management agreement	1 year
Period allowed for termination of automatic renewal of management agreement	60 days
Fee and other income from related parties (in US dollars)	$ 203	$ 203	$ 300