Segment Reporting Net Real Estate and Secured Note Payable Balances for Each Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Net real estate	$ 2,681,981	$ 2,492,734
Secured Notes Payable	111,000	111,000
Capital Expenditures and Leasing Commissions	107,730	69,077
Total Retail
Segment Reporting Information [Line Items]
Net real estate	591,107	607,918
Secured Notes Payable	0	0
Capital Expenditures and Leasing Commissions	7,232	8,596
Total Office
Segment Reporting Information [Line Items]
Net real estate	1,536,212	1,317,107
Secured Notes Payable	111,000	111,000
Capital Expenditures and Leasing Commissions	93,116	52,882
Total Multifamily
Segment Reporting Information [Line Items]
Net real estate	381,315	389,804
Capital Expenditures and Leasing Commissions	5,841	3,897
Total Mixed-Use
Segment Reporting Information [Line Items]
Net real estate	173,347	177,905
Capital Expenditures and Leasing Commissions	1,541	3,702
American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Net real estate	2,681,981	2,492,734
Secured notes payable | American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Debt issuance costs, net of accumulated amortization of $2,070 and $0, respectively	$ 35	$ 77