Consolidated Statement of Changes in Equity (USD $) In Thousands, except Share data	Total	Common Stock	Additional Capital	Retained Earnings	Accumulated Other Comprehensive Income	Treasury Stock	Alexander's Equity	Non-controlling Interest
Balance, at Dec. 31, 2009	$ 314,626	$ 5,173	$ 31,501	$ 275,921	$ 0	$ (375)	$ 312,220	$ 2,406
Shares Issued, Beginning Balance (in shares) at Dec. 31, 2009	5,173,000
Net income	67,445			66,429			66,429	1,016
Dividends paid	(38,295)			(38,295)			(38,295)
Change in unrealized net gain on securities available-for-sale	0
Balance, at Dec. 31, 2010	343,776	5,173	31,501	304,055	0	(375)	340,354	3,422
Shares Issued, Ending Balance (in shares) at Dec. 31, 2010	5,173,000
Net income	81,046			79,423			79,423	1,623
Dividends paid	(61,277)			(61,277)			(61,277)
Change in unrealized net gain on securities available-for-sale	0
Distributions	(600)							(600)
Deferred stock unit grant	300		300				300
Balance, at Dec. 31, 2011	363,245	5,173	31,801	322,201	0	(375)	358,800	4,445
Shares Issued, Ending Balance (in shares) at Dec. 31, 2011	5,173,450
Net income	674,993			674,387			674,387	606
Dividends paid	(699,791)			(699,791)			(699,791)
Acquisition of the noncontrolling interest	(7,800)		(2,749)				(2,749)	(5,051)
Change in unrealized net gain on securities available-for-sale	1,206				1,206		1,206
Deferred stock unit grant	300		300				300
Balance, at Dec. 31, 2012	$ 332,153	$ 5,173	$ 29,352	$ 296,797	$ 1,206	$ (375)	$ 332,153	$ 0
Shares Issued, Ending Balance (in shares) at Dec. 31, 2012	5,173,450