DEBT - Summary of Total Unsecured Notes Payable Outstanding (Details)	Jul. 18, 2024 USD ($)	Jan. 05, 2023 USD ($) extension	Jan. 05, 2022 USD ($) extension	Jul. 17, 2019 USD ($)	Jun. 23, 2017 USD ($)	May 11, 2017 USD ($)	Jan. 18, 2017 USD ($)	Jun. 30, 2024 USD ($) interest_rate_swap_agreement	Jan. 05, 2024	Dec. 31, 2023 USD ($)	Jan. 26, 2021 USD ($)	Jul. 30, 2019 USD ($)	Jul. 19, 2017 USD ($)	May 23, 2017 USD ($)	Mar. 01, 2017 USD ($)
Debt Instrument [Line Items]
Accumulated amortization								$ 1,620,000		$ 1,296,000
Debt discount and issuance costs, net of accumulated amortization of $8,561 and $7,259, respectively								(971,000)		(1,295,000)
American Assets Trust, L.P. | Treasury Lock
Debt Instrument [Line Items]
Loss on derivatives					$ 500,000
Gain on derivatives							$ 10,400,000
American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Gain on derivatives				$ 500,000		$ 700,000
Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Accumulated amortization								8,561,000		7,259,000
Principal Balance as of								1,625,000,000		1,625,000,000
Debt discount and issuance costs, net of accumulated amortization of $8,561 and $7,259, respectively								(8,741,000)		(10,042,000)
Total Secured Notes Payable Outstanding								$ 1,616,259,000		1,614,958,000
Term Loan A | American Assets Trust, L.P. | Interest Rate Swap
Debt Instrument [Line Items]
Number of interest rate | interest_rate_swap_agreement								2
Fixed interest rate on derivative								2.70%	2.70%
Term Loan A | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Principal Balance as of								$ 100,000,000		100,000,000
Term Loan B | American Assets Trust, L.P.
Debt Instrument [Line Items]
Face amount of debt		$ 150,000,000
Term Loan B | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Principal Balance as of								150,000,000		150,000,000
Face amount of debt		150,000,000
Term Loan C | American Assets Trust, L.P.
Debt Instrument [Line Items]
Face amount of debt		75,000,000
Term Loan C | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Principal Balance as of								$ 75,000,000		75,000,000
Face amount of debt		$ 75,000,000
Senior Guaranteed Notes, Series F | American Assets Trust, L.P. | Treasury Lock
Debt Instrument [Line Items]
Effective interest rate (percent)								3.85%
Senior Guaranteed Notes, Series F | Unsecured term loans, net | Subsequent Event
Debt Instrument [Line Items]
Borrowings	$ 100,000,000
Senior Guaranteed Notes, Series F | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate								3.78%					3.78%
Principal Balance as of								$ 100,000,000		100,000,000
Face amount of debt													$ 100,000,000
Senior Guaranteed Notes, Series F | Unsecured term loans, net | American Assets Trust, L.P. | Subsequent Event
Debt Instrument [Line Items]
Borrowings	$ 100,000,000
Senior Guaranteed Notes, Series B | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate								4.45%
Principal Balance as of								$ 100,000,000		100,000,000
Senior Guaranteed Notes, Series C | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate								4.50%
Principal Balance as of								$ 100,000,000		100,000,000
Senior Guaranteed Notes, Series D | American Assets Trust, L.P. | Treasury Lock
Debt Instrument [Line Items]
Effective interest rate (percent)								3.87%
Senior Guaranteed Notes, Series D | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate								4.29%							4.29%
Principal Balance as of								$ 250,000,000		250,000,000
Face amount of debt															$ 250,000,000
Senior Guaranteed Notes, Series E | American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Effective interest rate (percent)								4.18%
Senior Guaranteed Notes, Series E | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate								4.24%						4.24%
Principal Balance as of								$ 100,000,000		100,000,000
Face amount of debt														$ 100,000,000
Senior Guaranteed Notes, Series G | American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Effective interest rate (percent)								3.88%
Senior Guaranteed Notes, Series G | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate								3.91%				3.91%
Principal Balance as of								$ 150,000,000		150,000,000
Face amount of debt												$ 150,000,000
3.375% Senior Notes | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate								3.375%			3.375%
Principal Balance as of								$ 500,000,000		$ 500,000,000
Face amount of debt											$ 500,000,000
Term Loan B & Term Loan C | American Assets Trust, L.P.
Debt Instrument [Line Items]
Number of extensions available | extension		1
Extension term		12 months
Term Loan B & Term Loan C | American Assets Trust, L.P. | Interest Rate Swap | First period
Debt Instrument [Line Items]
Fixed interest rate on derivative		5.47%
Term Loan B & Term Loan C | American Assets Trust, L.P. | Interest Rate Swap | Second period
Debt Instrument [Line Items]
Fixed interest rate on derivative		5.57%
Term Loan B & Term Loan C | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Number of extensions available | extension		1
Extension term		12 months
Third Amended and Restated Credit Facility | American Assets Trust, L.P.
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity			$ 500,000,000
Third Amended and Restated Credit Facility | Unsecured term loans, net | American Assets Trust, L.P.
Debt Instrument [Line Items]
Number of extensions available | extension			2
Extension term			6 months
Revolving credit facility borrowing limit, maximum borrowing capacity			$ 100,000,000
Third Amended and Restated Credit Facility | Unsecured line of credit, net | American Assets Trust, L.P. | Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity			$ 400,000,000