EQUITY OF AMERICAN ASSETS TRUST, INC. - Computation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity [Abstract]
Net income from operations	$ 11,858	$ 19,026	$ 33,229	$ 42,689
Less: Net income attributable to restricted shares	(42)	(32)	(128)	(115)
Less: Income from operations attributable to unitholders in the Operating Partnership	(3,342)	(5,432)	(9,377)	(12,277)
Net income attributable to common stockholders—basic	8,474	13,562	23,724	30,297
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	8,474	13,562	23,724	30,297
Plus: Income from operations attributable to unitholders in the Operating Partnership	3,342	5,432	9,377	12,277
Net income attributable to common stockholders-diluted	$ 11,816	$ 18,994	$ 33,101	$ 42,574
Weighted average common shares outstanding-basic (in shares)	45,377,719	44,998,281	45,282,643	44,176,007
Effect of dilutive securities-conversion of Operating Partnership units (in shares)	17,894,983	17,899,516	17,897,994	17,900,231
Weighted average common shares outstanding - diluted (in shares)	63,272,702	62,897,797	63,180,637	62,076,238
Earnings per common share, basic (in USD per share)	$ 0.19	$ 0.30	$ 0.52	$ 0.69
Earnings per common share, diluted (in USD per share)	$ 0.19	$ 0.30	$ 0.52	$ 0.69