DEBT - Summary of Total Unsecured Notes Payable Outstanding (Details)	Jan. 05, 2023 USD ($) extension	Jul. 17, 2019 USD ($)	Jun. 23, 2017 USD ($)	May 11, 2017 USD ($)	Jan. 18, 2017 USD ($)	Mar. 31, 2024 USD ($) 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]
Debt issuance costs, accumulated amortization						$ 1,458,000		$ 1,296,000
Debt discount and issuance costs, net of accumulated amortization of $7,910 and $7,259, respectively						(1,133,000)		(1,295,000)
American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Debt issuance costs, accumulated amortization						7,910,000		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 $7,910 and $7,259, respectively						(9,392,000)		(10,042,000)
Total Secured Notes Payable Outstanding						1,615,608,000		1,614,958,000
American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Gain on derivatives		$ 500,000		$ 700,000
American Assets Trust, L.P. | Treasury Lock
Debt Instrument [Line Items]
Loss on derivatives			$ 500,000
Gain on derivatives					$ 10,400,000
Term Loan A | American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 100,000,000		100,000,000
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 B | American Assets Trust, L.P.
Debt Instrument [Line Items]
Face amount of debt	$ 150,000,000
Term Loan B | American Assets Trust, L.P. | Unsecured term loans, net
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 | American Assets Trust, L.P. | Unsecured term loans, net
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. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 100,000,000		100,000,000
Stated Interest Rate						3.78%					3.78%
Face amount of debt											$ 100,000,000
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 B | American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 100,000,000		100,000,000
Stated Interest Rate						4.45%
Senior Guaranteed Notes, Series C | American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 100,000,000		100,000,000
Stated Interest Rate						4.50%
Senior Guaranteed Notes, Series D | American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 250,000,000		250,000,000
Stated Interest Rate						4.29%							4.29%
Face amount of debt													$ 250,000,000
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 E | American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 100,000,000		100,000,000
Stated Interest Rate						4.24%						4.24%
Face amount of debt												$ 100,000,000
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 G | American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 150,000,000		150,000,000
Stated Interest Rate						3.91%				3.91%
Face amount of debt										$ 150,000,000
Senior Guaranteed Notes, Series G | American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Effective interest rate (percent)						3.88%
3.375% Senior Notes | American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Principal Balance as of						$ 500,000,000		$ 500,000,000
Stated Interest Rate						3.375%			3.375%
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. | Unsecured term loans, net
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%