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 ($)	Dec. 31, 2023 USD ($) interest_rate_swap_agreement	Dec. 31, 2022 USD ($)	Jan. 14, 2022	Jan. 26, 2021 USD ($)	Jul. 30, 2019 USD ($)	Jul. 19, 2017 USD ($)	May 23, 2017 USD ($)	Mar. 01, 2017 USD ($)
Debt Instrument [Line Items]
Total Unsecured Notes Payable						$ 1,614,958,000	$ 1,539,453,000
American Assets Trust, L.P.
Debt Instrument [Line Items]
Total Unsecured Notes Payable						1,614,958,000	1,539,453,000
American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Principal Balance as of						1,625,000,000	1,550,000,000
Debt discount and issuance costs, net of accumulated amortization of $7,259 and $11,709, respectively						(10,042,000)	(10,547,000)
Total Unsecured Notes Payable						1,614,958,000	1,539,453,000
Debt issuance costs, accumulated amortization						7,259,000	11,709,000
American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Loss on derivatives			$ 500,000
Gain on derivatives		$ 500,000		$ 700,000	$ 10,400,000
Term Loan A | American Assets Trust, L.P. | Unsecured Debt
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 Debt
Debt Instrument [Line Items]
Principal Balance as of						$ 150,000,000	100,000,000
Face amount of debt	150,000,000
Term Loan B | American Assets Trust, L.P. | Interest Rate Swap | First period
Debt Instrument [Line Items]
Fixed interest rate on derivative						5.47%
Term Loan B | American Assets Trust, L.P. | Interest Rate Swap | Second period
Debt Instrument [Line Items]
Fixed interest rate on derivative						5.57%
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 Debt
Debt Instrument [Line Items]
Principal Balance as of						$ 75,000,000	50,000,000
Face amount of debt	$ 75,000,000
Term Loan C | American Assets Trust, L.P. | Interest Rate Swap | First period
Debt Instrument [Line Items]
Fixed interest rate on derivative						5.57%
Term Loan C | American Assets Trust, L.P. | Interest Rate Swap | Second period
Debt Instrument [Line Items]
Fixed interest rate on derivative						5.47%
Senior Guaranteed Notes, Series F | American Assets Trust, L.P. | Unsecured Debt
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. | Forward Contracts
Debt Instrument [Line Items]
Effective interest rate (percent)						3.85%
Senior Guaranteed Notes, Series B | American Assets Trust, L.P. | Unsecured Debt
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 Debt
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 Debt
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. | Forward Contracts
Debt Instrument [Line Items]
Effective interest rate (percent)						3.87%
Senior Guaranteed Notes, Series E | American Assets Trust, L.P. | Unsecured Debt
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 Debt
Debt Instrument [Line Items]
Principal Balance as of							150,000,000			$ 150,000,000
Stated Interest Rate						3.91%				3.91%
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 Unsecured Notes | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Interest Rate						3.375%			3.375%
3.375% Senior Unsecured Notes | American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Principal Balance as of						$ 500,000,000	500,000,000
Stated Interest Rate						3.38%
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 Debt
Debt Instrument [Line Items]
Number of extensions available | extension	1
Extension term	12 months
Face amount of debt						$ 225,000,000	$ 150,000,000
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%