EQUITY OF AMERICAN ASSETS TRUST, INC. - Computation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Equity [Abstract]
Net income from operations	$ 12,284	$ 5,351	$ 23,663	$ 12,009
Less: Net income attributable to restricted shares	(40)	(94)	(83)	(164)
Less: Income from continuing operations attributable to unitholders in the Operating Partnership	(3,536)	(1,544)	(6,845)	(3,530)
Net income attributable to common stockholders—basic	8,708	3,713	16,735	8,315
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	8,708	3,713	16,735	8,315
Net income attributable to common stockholders-diluted	$ 12,244	$ 5,257	$ 23,580	$ 11,845
Weighted average common shares outstanding-basic	44,092,631	41,816,379	43,758,055	41,202,993
Effect of dilutive securities-conversion of Operating Partnership units	17,899,516	17,905,257	17,900,595	17,907,457
Weighted average common shares outstanding - diluted	61,992,147	59,721,636	61,658,650	59,110,450
Earnings per common share, basic	$ 0.20	$ 0.09	$ 0.38	$ 0.20
Earnings per common share, diluted	$ 0.20	$ 0.09	$ 0.38	$ 0.20