EQUITY OF AMERICAN ASSETS TRUST, INC. - Narrative (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Dec. 03, 2021 USD ($) sales_agent	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) shares	Dec. 31, 2020 USD ($) shares
Equity [Line Items]
Preferred stock, shares authorized (in shares)		10,000,000
Preferred stock, par-value (in dollars per share) | $ / shares		$ 0.01
Preferred stock, shares issued (in shares)		0
Equity incentive award plan, common stock authorized for issuance (in shares)		4,054,411
Equity incentive award plan, common stock available for future issuance (in shares)		2,183,962
Look back period		3 years
Noncash compensation expense | $		$ 8.7	$ 8.5	$ 6.3
Unrecognized compensation expense | $		$ 9.4
American Assets Trust, L.P.
Equity [Line Items]
Antidilutive securities excluded from computation of EPS (in shares)		489,765	485,202	357,048
Restricted Stock
Equity [Line Items]
Vesting period		3 years
Unrecognized compensation expense, weighted-average recognition period (in years)		1 year 6 months 7 days
Restricted Stock | Share-Based Payment Arrangement, Tranche One
Equity [Line Items]
Performance period		1 year
Restricted Stock | Share-Based Payment Arrangement, Tranche Two
Equity [Line Items]
Performance period		2 years
Restricted Stock | Share-Based Payment Arrangement, Tranche Three
Equity [Line Items]
Performance period		3 years
At The Market Equity Program
Equity [Line Items]
Aggregate offering price of common share | $	$ 250.0
Common shares issued (in shares)		0
Remaining capacity available for issuance | $		$ 250.0
$250.0 Million ATM | At The Market Equity Program
Equity [Line Items]
Number of sales agents | sales_agent	5
Operating Partnership Units | American Assets Trust, L.P.
Equity [Line Items]
Weighted average unvested shares outstanding (in shares)		489,765	485,202	357,048