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SEGMENT REPORTING - Summary of Net Real Estate and Secured Note Payable Balances by Segments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Segment Reporting Information [Line Items]
Net Real Estate	$ 2,626,930		$ 2,626,930		$ 2,587,486
Secured Notes Payable	75,000		75,000		75,000
Debt issuance costs	162		162		648
Capital Expenditures	19,233	$ 26,339	59,519	$ 56,763
American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Net Real Estate	2,626,930		2,626,930		2,587,486
Secured notes payable, net | American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Debt issuance costs	173		173		241
Office
Segment Reporting Information [Line Items]
Net Real Estate	1,588,085		1,588,085		1,597,458
Secured Notes Payable	75,000		75,000		75,000
Capital Expenditures	13,185	20,261	47,354	41,930
Retail
Segment Reporting Information [Line Items]
Net Real Estate	472,969		472,969		478,037
Capital Expenditures	4,500	4,267	7,146	9,651
Multifamily
Segment Reporting Information [Line Items]
Net Real Estate	408,395		408,395		351,016
Capital Expenditures	1,110	1,582	3,072	4,260
Mixed-Use
Segment Reporting Information [Line Items]
Net Real Estate	157,481		157,481		$ 160,975
Capital Expenditures	$ 438	$ 229	$ 1,947	$ 922

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Including the current and noncurrent portions, aggregate carrying amount of all types of notes payable, as of the balance sheet date, with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Amount of real estate investment property, net of accumulated depreciation, which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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