SEGMENT REPORTING - Net Real Estate and Secured Note Payable Balances (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Real estate, net	$ 2,731,457	$ 2,681,981
Secured Notes Payable	111,000	111,000
Debt issuance costs, net of accumulated amortization of $2,232 and $2,070, respectively	2,430	0
American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Real estate, net	2,731,457	2,681,981
Secured notes payable, net \| American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Debt issuance costs, net of accumulated amortization of $2,232 and $2,070, respectively	24	35
Office
Segment Reporting Information [Line Items]
Real estate, net	1,590,488	1,536,212
Secured Notes Payable	111,000	111,000
Retail
Segment Reporting Information [Line Items]
Real estate, net	590,113	591,107
Multifamily
Segment Reporting Information [Line Items]
Real estate, net	378,887	381,315
Mixed-use
Segment Reporting Information [Line Items]
Real estate, net	$ 171,969	$ 173,347

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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