SEGMENT REPORTING - Net Real Estate and Secured Note Payable Balances (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Real estate, net	$ 2,715,269	$ 2,734,556
Secured Notes Payable	75,000	75,000
Debt issuance costs	1,457	0
American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Real estate, net	2,715,269	2,734,556
Secured notes payable, net \| American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Debt issuance costs	354	422
Office
Segment Reporting Information [Line Items]
Real estate, net	1,616,638	1,615,479
Secured Notes Payable	75,000	75,000
Retail
Segment Reporting Information [Line Items]
Real estate, net	567,354	579,219
Multifamily
Segment Reporting Information [Line Items]
Real estate, net	363,750	370,993
Mixed-use
Segment Reporting Information [Line Items]
Real estate, net	$ 167,527	$ 168,865

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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-Publisher FASB
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
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-Publisher FASB
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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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.5-02(22))
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
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-Section S99
-Paragraph 1
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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.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 210
-Name Accounting Standards Codification
-Section S99
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