EQUITY Computation of Basic and Diluted EPS (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Equity [Abstract]
Income from continuing operations	$ 9,090	$ 6,258	$ 21,099	$ 15,687
Less: Net income attributable to restricted shares	(95)	(132)	(259)	(397)
Less: Income from continuing operations attributable to unitholders in the Operating Partnership	(2,578)	(1,903)	(6,108)	(4,752)
Net income attributable to common stockholders—basic	6,417	4,223	14,732	10,538
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	6,417	4,223	14,732	10,538
Net income attributable to common stockholders-diluted	$ 8,995	$ 6,126	$ 20,840	$ 15,290
Weighted average common shares outstanding-basic	42,539,019	39,816,753	41,653,229	39,439,488
Effect of dilutive securities-conversion of Operating Partnership units	17,905,257	17,960,914	17,906,715	17,984,471
Weighted average common shares outstanding - diluted	60,444,276	57,777,667	59,559,944	57,423,959
Earnings per common share, basic	$ 0.15	$ 0.11	$ 0.35	$ 0.27
Earnings per common share, diluted	$ 0.15	$ 0.11	$ 0.35	$ 0.27