EQUITY OF AMERICAN ASSETS TRUST, INC. - Computation of Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
NUMERATOR
Net income	$ 13,492	$ 15,135	$ 15,397	$ 20,666	$ 12,406	$ 16,369	$ 13,588	$ 13,514	$ 64,690	$ 55,877	$ 36,593
Less: Net income attributable to restricted shares	(193)	(189)	(190)	(189)	(184)	(155)	(154)	(155)	(761)	(648)	(564)
Less: Income attributable to unitholders in the Operating Partnership	$ (2,818)	$ (3,168)	$ (3,224)	$ (4,341)	$ (2,593)	$ (3,442)	$ (2,852)	$ (2,836)	(13,551)	(11,723)	(7,653)
NET INCOME ATTRIBUTABLE TO AMERICAN ASSETS TRUST, INC. STOCKHOLDERS									50,378	43,506	28,376
Net income attributable to American Assets Trust, Inc. stockholders									50,378	43,506	28,376
Plus: Income attributable to unitholders in the Operating Partnership									13,551	11,723	7,653
Net income attributable to common stockholders—diluted									$ 63,929	$ 55,229	$ 36,029
DENOMINATOR
Weighted average shares of common stock outstanding-basic (in shares)									60,158,976	60,048,970	59,990,740
Effect of dilutive securities-conversion of Operating Partnership units (in shares)									16,181,537	16,181,537	16,181,537
Weighted average common shares outstanding - diluted (in shares)									76,340,513	76,230,507	76,172,277
EARNINGS PER COMMON SHARE, BASIC
Basic income attributable to common stockholders per share (in USD per share)	$ 0.17	$ 0.20	$ 0.20	$ 0.27	$ 0.16	$ 0.21	$ 0.18	$ 0.18	$ 0.84	$ 0.72	$ 0.47
EARNINGS PER COMMON SHARE, DILUTED
Diluted income attributable to common stockholders per share (in USD per share)	$ 0.17	$ 0.20	$ 0.20	$ 0.27	$ 0.16	$ 0.21	$ 0.18	$ 0.18	$ 0.84	$ 0.72	$ 0.47