Related Party Transactions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Urban Edge Properties
Related Party Transaction
Percentage of affiliated entity owned by company	4.50%
Alexanders Inc
Related Party Transaction
Percentage of affiliated entity owned by company	32.40%
Percentage of affiliated entity owned by related parties	26.20%
Interstate Properties
Related Party Transaction
Percentage of company owned by related party	7.10%
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)	$ 453	$ 501	$ 521