Related Party Transactions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Alexanders Inc [Member]
Related Party Transaction [Line Items]
Percentage of Affiliated Entity Owned By Company	32.40%
Percentage Of Affiliated Entity Owned By Related Parties	26.30%
Interstate Properties [Member]
Related Party Transaction [Line Items]
Percentage of Company Owned by Related Party	6.60%
Related Party Transaction Annual Fee Percentage	4.00%
Fee And Other Income From Related Parties (in US dollars)	$ 606	$ 794	$ 787
Related Party Transaction Description Of Transaction	We manage and lease the real estate assets of Interstate pursuant to a management agreement for which we receive an annual fee equal to 4% of annual base rent and percentage rent. The management agreement has a term of one year and is automatically renewable unless terminated by either of the parties on 60 days’ notice at the end of the term. We believe, based upon comparable fees charged by other real estate companies, that the management agreement terms are fair to us.