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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Net income from operations	$ 10,650	$ 12,284	$ 21,371	$ 23,663
Less: Net income attributable to restricted shares	(43)	(40)	(86)	(83)
Less: Income from operations attributable to unitholders in the Operating Partnership	(3,008)	(3,536)	(6,035)	(6,845)
Net income attributable to common stockholders—basic	7,599	8,708	15,250	16,735
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	7,599	8,708	15,250	16,735
Plus: Income from operations attributable to unitholders in the Operating Partnership	3,008	3,536	6,035	6,845
Net income attributable to common stockholders-diluted	$ 10,607	$ 12,244	$ 21,285	$ 23,580
Weighted average common shares outstanding-basic	45,235,292	44,092,631	45,234,583	43,758,055
Effect of dilutive securities-conversion of Operating Partnership units	17,899,516	17,899,516	17,899,516	17,900,595
Weighted average common shares outstanding - diluted	63,134,808	61,992,147	63,134,099	61,658,650
Earnings per common share, basic (in USD per share)	$ 0.17	$ 0.20	$ 0.34	$ 0.38
Earnings per common share, diluted (in USD per share)	$ 0.17	$ 0.20	$ 0.34	$ 0.38