DEBT - Summary of Total Unsecured Notes Payable Outstanding (Details)	Jan. 05, 2023 USD ($) extension	Oct. 01, 2020 USD ($)	Jul. 17, 2019 USD ($)	Jan. 09, 2019 extension	Jun. 23, 2017 USD ($)	May 11, 2017 USD ($)	Jan. 18, 2017 USD ($)	Jan. 04, 2023 USD ($)	Dec. 31, 2022 USD ($) interest_rate_swap_agreement	Nov. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jan. 26, 2021 USD ($)	Jul. 30, 2019 USD ($)	Nov. 26, 2018	Mar. 01, 2018	Jan. 09, 2018 USD ($)	Jul. 19, 2017 USD ($)	May 23, 2017 USD ($)	Mar. 01, 2017 USD ($)	May 02, 2016 USD ($)	Mar. 23, 2016 USD ($)	Mar. 01, 2016 USD ($)	Jan. 29, 2016 USD ($)	Jan. 09, 2014 USD ($)
Debt Instrument [Line Items]
Total Unsecured Notes Payable									$ 1,539,453,000		$ 1,538,238,000
American Assets Trust, L.P.
Debt Instrument [Line Items]
Total Unsecured Notes Payable									1,539,453,000		1,538,238,000
American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Principal Balance as of									1,550,000,000		1,550,000,000
Debt discount and issuance costs, net of accumulated amortization of $11,709 and $9,462, respectively									(10,547,000)		(11,762,000)
Total Unsecured Notes Payable									1,539,453,000		1,538,238,000
Debt issuance costs, accumulated amortization									11,709,000		9,462,000
American Assets Trust, L.P. | Interest Rate Swap
Debt Instrument [Line Items]
Gain on derivatives		$ 0
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.
Debt Instrument [Line Items]
Total Unsecured Notes Payable																								$ 100,000,000
Face amount of debt										$ 225,000,000
Term Loan A | American Assets Trust, L.P. | Subsequent Event
Debt Instrument [Line Items]
Face amount of debt	$ 225,000,000
Term Loan A | American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Principal Balance as of									$ 100,000,000		100,000,000
Number of extensions available | extension				3
Extension term				1 year
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%					4.13%
Term Loan B & Term Loan C | Unsecured Debt | Subsequent Event
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. | Subsequent Event
Debt Instrument [Line Items]
Number of extensions available | extension	1
Extension term	12 months
Face amount of debt	$ 75,000,000							150,000,000
Term Loan B & Term Loan C | American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt																$ 150,000,000
Term Loan B & Term Loan C | American Assets Trust, L.P. | Unsecured Debt | Subsequent Event
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 | American Assets Trust, L.P.
Debt Instrument [Line Items]
Face amount of debt																						$ 100,000,000	$ 100,000,000
Term Loan B | American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Principal Balance as of									$ 100,000,000		100,000,000
Face amount of debt																						$ 100,000,000
Term Loan B | American Assets Trust, L.P. | Interest Rate Swap
Debt Instrument [Line Items]
Fixed interest rate on derivative									3.15%						2.65%
Variable interest rate on derivative									5.32%
Term Loan B | American Assets Trust, L.P. | Interest Rate Swap | Unsecured Debt
Debt Instrument [Line Items]
Fixed interest rate on derivative																						3.15%
Term Loan C | American Assets Trust, L.P.
Debt Instrument [Line Items]
Face amount of debt																				$ 50,000,000	$ 50,000,000
Term Loan C | American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Principal Balance as of									$ 50,000,000		50,000,000
Face amount of debt																				$ 50,000,000
Term Loan C | American Assets Trust, L.P. | Interest Rate Swap
Debt Instrument [Line Items]
Fixed interest rate on derivative									3.14%						2.64%							3.14%
Variable interest rate on derivative									5.32%
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