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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Equity [Abstract]
Net income from operations	$ 7,588	$ 10,650	$ 17,896	$ 21,371
Less: Net income attributable to restricted shares	(61)	(43)	(121)	(86)
Less: Income from operations attributable to unitholders in the Operating Partnership	(2,008)	(3,008)	(4,869)	(6,035)
Net income attributable to common stockholders—basic	5,519	7,599	12,906	15,250
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	5,519	7,599	12,906	15,250
Plus: Income from operations attributable to unitholders in the Operating Partnership	2,008	3,008	4,869	6,035
Net income attributable to common stockholders-diluted	$ 7,527	$ 10,607	$ 17,775	$ 21,285
Weighted average common shares outstanding-basic (in shares)	46,871,377	45,235,292	46,524,510	45,234,583
Effect of dilutive securities-conversion of Operating Partnership units (in shares)	17,217,704	17,899,516	17,551,409	17,899,516
Weighted average common shares outstanding - diluted (in shares)	64,089,081	63,134,808	64,075,919	63,134,099
Earnings per common share, basic (in USD per share)	$ 0.12	$ 0.17	$ 0.28	$ 0.34
Earnings per common share, diluted (in USD per share)	$ 0.12	$ 0.17	$ 0.28	$ 0.34