EQUITY Computation of Basic and Diluted EPS (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Equity [Abstract]
Income from continuing operations	$ 4,564	$ 2,397	$ 9,429	$ 5,161
Less: Net income attributable to restricted shares	(133)	(131)	(265)	(263)
Less: Income from continuing operations attributable to unitholders in the Operating Partnership	(1,354)	(804)	(2,849)	(1,687)
Income from continuing operations attributable to American Assets Trust, Inc. common stockholders-basic	3,077	1,462	6,315	3,211
Plus: Results from discontinued operations attributable to American Assets Trust, Inc. common stockholders	0	154	0	226
Income from continuing operations attributable to American Assets Trust, Inc. common stockholders-basic	3,077	1,616	6,315	3,437
Income from continuing operations attributable to common stockholders-diluted	4,431	2,266	9,164	4,898
Plus: Results from discontinued operations attributable to unitholders in the Operating Partnership	0	73	0	108
Net income attributable to common stockholders-diluted	$ 4,431	$ 2,493	$ 9,164	$ 5,232
Weighted average common shares outstanding-basic	39,460,086	38,659,155	39,247,729	38,658,162
Effect of dilutive securities-conversion of Operating Partnership units	17,969,751	18,396,089	17,996,445	18,396,347
Weighted average common shares outstanding - diluted	57,429,837	57,055,244	57,244,174	57,054,509
Continuing operations	$ 0.08	$ 0.04	$ 0.16	$ 0.08
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.01
Basic net income attributable to common stockholders per share	$ 0.08	$ 0.04	$ 0.16	$ 0.09
Continuing operations	$ 0.08	$ 0.04	$ 0.16	$ 0.08
Discontinued operations	$ 0.00	$ 0.00	$ 0.00	$ 0.01
Diluted net income attributable to common stockholders per share	$ 0.08	$ 0.04	$ 0.16	$ 0.09