Equity (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Numerator
Income from continuing operations	$ 2,624	$ (7)	$ 5,495	$ 13,259
Less: Net income attributable to restricted shares	(131)	(132)	(263)	(218)
Plus: Loss from continuing operations attributable to Predecessor's noncontrolling interests in consolidated real estate entities				2,454
Less: Income from continuing operations attributable to Predecessor's controlled owners' equity				(17,009)
Less: loss from continuing operations attributable to unitholders in the Operating Partnership	(804)	46	(1,687)	488
Income (loss) from continuing operations attributable to American Assets Trust Inc. common stockholders'-basic	1,689	(93)	3,545	(1,026)
Plus: Results from discontinued operations attributable to American Assets Trust Inc. common stockholders		312		547
Net income (loss) attributable to common stockholders-basic	1,689	219	3,545	(479)
Income (loss) from continuing operations attributable to American Assets Trust, Inc. common stockholders-basic	1,689	219	3,545	(479)
Plus: Income (loss) from continuing operations attributable to unitholders in the Operating Partnership	804	(46)	1,687	(488)
Income (loss) from continuing operations attributable to common stockholders-diluted	2,493	(139)	5,232	(1,026)
Plus: Results from discontinued operations attributable to unitholders in the Operating Partnership		150
Net income (loss) attributable to common stockholders-diluted	$ 2,493	$ 323	$ 5,232	$ (479)
Denominator
Weighted average common shares outstanding-basic	38,659,155	38,655,084	38,658,162	34,810,932
Effect of dilutive securities-conversion of Operating Partnership units	18,396,089	18,396,089	18,396,347
Weighted average common shares outstanding - diluted	57,055,244	57,051,173	57,054,509	34,810,932
Earnings (loss) per common share - basic
Continuing operations	$ 0.04		$ 0.09	$ (0.03)
Discontinued operations		$ 0.01		$ 0.02
Earnings per share-basic, Total	$ 0.04	$ 0.01	$ 0.09	$ (0.01)
Earnings (loss) per common share - diluted
Continuing operations	$ 0.04		$ 0.09	$ (0.03)
Discontinued operations		$ 0.01		$ 0.02
Earnings per share-diluted, Total	$ 0.04	$ 0.01	$ 0.09	$ (0.01)