EQUITY OF AMERICAN ASSETS TRUST, INC. - Computation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Equity [Abstract]
Net income from operations	$ 10,308	$ 10,721
Less: Net income attributable to restricted shares	(60)	(43)
Less: Income from operations attributable to unitholders in the Operating Partnership	(2,861)	(3,027)
Net income attributable to common stockholders—basic	7,387	7,651
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	7,387	7,651
Plus: Income from operations attributable to unitholders in the Operating Partnership	2,861	3,027
Net income attributable to common stockholders-diluted	$ 10,248	$ 10,678
Weighted average common shares outstanding-basic (in shares)	46,173,788	45,233,873
Effect of dilutive securities-conversion of Operating Partnership units (in shares)	17,888,822	17,899,516
Weighted average common shares outstanding - diluted (in shares)	64,062,610	63,133,389
Earnings per common share, basic (in USD per share)	$ 0.16	$ 0.17
Earnings per common share, diluted (in USD per share)	$ 0.16	$ 0.17