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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity [Abstract]
Net income	$ 9,826	$ 11,941	$ 25,310	$ 27,184
Less: Net income attributable to restricted shares	(69)	(92)	(173)	(185)
Less: Income from operations attributable to unitholders in the Operating Partnership	(2,101)	(2,933)	(5,413)	(6,988)
Net income attributable to common stockholders—basic	7,656	8,916	19,724	20,011
Income from operations attributable to American Assets Trust, Inc. common stockholders—basic	7,656	8,916	19,724	20,011
Plus: Income from operations attributable to unitholders in the Operating Partnership-diluted	2,101	2,933	5,413	6,988
Net income attributable to common stockholders-diluted	$ 9,757	$ 11,849	$ 25,137	$ 26,999
Weighted average common shares outstanding-basic (in shares)	59,724,139	50,135,978	59,723,605	48,578,872
Effect of dilutive securities-conversion of Operating Partnership units (in shares)	16,390,548	16,753,806	16,390,548	16,964,537
Weighted average common shares outstanding - diluted (in shares)	76,114,687	66,889,784	76,114,153	65,543,409
Earnings per common share, basic (in USD per share)	$ 0.13	$ 0.18	$ 0.33	$ 0.41
Earnings per common share, diluted (in USD per share)	$ 0.13	$ 0.18	$ 0.33	$ 0.41