QUARTERLY FINANCIAL INFORMATION (UNAUDITED) - Selected Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Quarterly Financial Information [Line Items]
Revenues	$ 106,000	$ 111,023	$ 104,155	$ 101,470	$ 101,747	$ 98,286	$ 91,809	$ 83,986	$ 422,648	$ 375,828	$ 344,573
Operating income (loss)	27,073	31,003	28,316	28,342	25,715	27,669	26,423	20,062	114,734	99,869	88,581
Net income	12,406	16,369	13,588	13,514	10,478	12,895	11,487	1,733	55,877	36,593	35,588
Net income attributable to restricted shares	(184)	(155)	(154)	(155)	(147)	(145)	(135)	(137)	(648)	(564)	(383)
Net income attributable to unitholders in the Operating Partnership	(2,593)	(3,442)	(2,852)	(2,836)	(2,194)	(2,709)	(2,411)	(339)	$ (11,723)	$ (7,653)	$ (7,545)
Net income attributable to American Assets Trust, Inc. stockholders	$ 9,629	$ 12,772	$ 10,582	$ 10,523	$ 8,137	$ 10,041	$ 8,941	$ 1,257
Net income per share attributable to common stockholders - basic (in USD per share)	$ 0.16	$ 0.21	$ 0.18	$ 0.18	$ 0.14	$ 0.17	$ 0.15	$ 0.02	$ 0.72	$ 0.47	$ 0.46
Net income per share attributable to common stockholders - diluted (in USD per share)	$ 0.16	$ 0.21	$ 0.18	$ 0.18	$ 0.14	$ 0.17	$ 0.15	$ 0.02	$ 0.72	$ 0.47	$ 0.46
American Assets Trust, L.P.
Quarterly Financial Information [Line Items]
Revenues	$ 106,000	$ 111,023	$ 104,155	$ 101,470	$ 101,747	$ 98,286	$ 91,809	$ 83,986	$ 422,648	$ 375,828	$ 344,573
Operating income (loss)	27,073	31,003	28,316	28,342	25,715	27,669	26,423	20,062	114,734	99,869	88,581
Net income	12,406	16,369	13,588	13,514	10,478	12,895	11,487	1,733	55,877	36,593	35,588
Net income attributable to restricted shares	(184)	(155)	(154)	(155)	(147)	(145)	(135)	(137)	$ (648)	$ (564)	$ (383)
Net income attributable to American Assets Trust, L.P. unit holders	$ 12,222	$ 16,214	$ 13,434	$ 13,359	$ 10,331	$ 12,750	$ 11,352	$ 1,596
Net income per share attributable to common stockholders - basic (in USD per share)	$ 0.16	$ 0.21	$ 0.18	$ 0.18	$ 0.14	$ 0.17	$ 0.15	$ 0.02	$ 0.72	$ 0.47	$ 0.46
Net income per share attributable to common stockholders - diluted (in USD per share)	$ 0.16	$ 0.21	$ 0.18	$ 0.18	$ 0.14	$ 0.17	$ 0.15	$ 0.02	$ 0.72	$ 0.47	$ 0.46