EQUITY OF AMERICAN ASSETS TRUST, INC. - Computation of Basic and Diluted EPS (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Equity [Abstract]
Net income from operations	$ 11,379	$ 6,658
Less: Net income attributable to restricted shares	(43)	(70)
Less: Income from continuing operations attributable to unitholders in the Operating Partnership	(3,309)	(1,986)
Net income attributable to common stockholders—basic	8,027	4,602
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	8,027	4,602
Net income attributable to common stockholders-diluted	$ 11,336	$ 6,588
Weighted average common shares outstanding-basic	43,419,762	40,582,792
Effect of dilutive securities-conversion of Operating Partnership units	17,901,685	17,909,681
Weighted average common shares outstanding - diluted	61,321,447	58,492,473
Earnings per common share, basic	$ 0.18	$ 0.11
Earnings per common share, diluted	$ 0.18	$ 0.11