DEBT - Summary of Total Unsecured Notes Payable Outstanding (Details)						1 Months Ended
	Jan. 05, 2023 USD ($) extension	Jul. 17, 2019 USD ($)	Jun. 23, 2017 USD ($)	May 11, 2017 USD ($)	Jan. 18, 2017 USD ($)	Jan. 04, 2023 USD ($)	Sep. 30, 2023 USD ($) interest_rate_swap_agreement	Dec. 31, 2022 USD ($)	Jan. 26, 2021 USD ($)	Mar. 01, 2018	Jan. 09, 2018 USD ($)
Debt Instrument [Line Items]
Debt discount and issuance costs, net of accumulated amortization of $6,609 and $11,709, respectively							$ (1,457,000)	$ 0
Debt issuance costs, accumulated amortization							1,134,000	0
American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Loss on derivative settlement			$ 500,000
Gain on derivative settlement		$ 500,000		$ 700,000	$ 10,400,000
American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							1,625,000,000	1,550,000,000
Debt discount and issuance costs, net of accumulated amortization of $6,609 and $11,709, respectively							(10,693,000)	(10,547,000)
Total Notes Payable							1,614,307,000	1,539,453,000
Debt issuance costs, accumulated amortization							$ 6,609,000	11,709,000
American Assets Trust, L.P. | Term Loan A | Interest Rate Swap
Debt Instrument [Line Items]
Number of interest rate swap agreements | interest_rate_swap_agreement							2
Derivative fixed interest rate							2.70%
American Assets Trust, L.P. | Term Loan A | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 100,000,000	100,000,000
American Assets Trust, L.P. | Term Loan B
Debt Instrument [Line Items]
Face amount of debt	$ 150,000,000
American Assets Trust, L.P. | Term Loan B | Interest Rate Swap
Debt Instrument [Line Items]
Interest rate during period						5.32%
American Assets Trust, L.P. | Term Loan B | Interest Rate Swap | First Year
Debt Instrument [Line Items]
Derivative fixed interest rate	5.47%									2.65%
American Assets Trust, L.P. | Term Loan B | Interest Rate Swap | Second Year
Debt Instrument [Line Items]
Derivative fixed interest rate	5.57%
American Assets Trust, L.P. | Term Loan B | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							150,000,000	100,000,000
American Assets Trust, L.P. | Term Loan C
Debt Instrument [Line Items]
Face amount of debt	$ 75,000,000
American Assets Trust, L.P. | Term Loan C | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate										2.64%
Interest rate during period						5.32%
American Assets Trust, L.P. | Term Loan C | Interest Rate Swap | First Year
Debt Instrument [Line Items]
Derivative fixed interest rate	5.47%
American Assets Trust, L.P. | Term Loan C | Interest Rate Swap | Second Year
Debt Instrument [Line Items]
Derivative fixed interest rate	5.57%
American Assets Trust, L.P. | Term Loan C | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 75,000,000	50,000,000
American Assets Trust, L.P. | Senior Guaranteed Notes, Series F | Forward Contracts
Debt Instrument [Line Items]
Effective rate of debt instrument							3.85%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series F | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 100,000,000	100,000,000
Stated Interest Rate							3.78%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series B | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 100,000,000	100,000,000
Stated Interest Rate							4.45%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series C | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 100,000,000	100,000,000
Stated Interest Rate							4.50%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D | Forward Contracts
Debt Instrument [Line Items]
Effective rate of debt instrument							3.87%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 250,000,000	250,000,000
Stated Interest Rate							4.29%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series E | Forward Contracts
Debt Instrument [Line Items]
Effective rate of debt instrument							4.18%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series E | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 100,000,000	100,000,000
Stated Interest Rate							4.24%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series G | Forward Contracts
Debt Instrument [Line Items]
Effective rate of debt instrument							3.88%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series G | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 150,000,000	150,000,000
Stated Interest Rate							3.91%
American Assets Trust, L.P. | 3.375% Senior Unsecured Notes
Debt Instrument [Line Items]
Stated Interest Rate									3.375%
American Assets Trust, L.P. | 3.375% Senior Unsecured Notes | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance							$ 500,000,000	$ 500,000,000
Stated Interest Rate							3.375%
Face amount of debt									$ 500,000,000
American Assets Trust, L.P. | Term Loan B & Term Loan C
Debt Instrument [Line Items]
Debt extension options | extension	1
Extension term	12 months
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured term loans, net
Debt Instrument [Line Items]
Debt extension options | extension	1
Extension term	12 months
Face amount of debt	$ 225,000,000					$ 150,000,000					$ 150,000,000