DEBT - Narrative (Details)															12 Months Ended
	Jan. 05, 2023 USD ($) extension	Nov. 30, 2022 USD ($)	Sep. 16, 2022 USD ($)	Jan. 05, 2022 USD ($) extension	Jan. 26, 2021 USD ($)	Jan. 09, 2019 extension	Jan. 09, 2018 USD ($) extension	Apr. 25, 2017	May 02, 2016 USD ($)	Mar. 23, 2016 USD ($)	Mar. 01, 2016 USD ($)	Jan. 29, 2016 USD ($)	Oct. 31, 2014 USD ($)	Jan. 09, 2014 USD ($) extension	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jan. 04, 2023 USD ($)	Jul. 30, 2019 USD ($)	Nov. 26, 2018	Mar. 01, 2018	Jul. 19, 2017 USD ($)	May 23, 2017 USD ($)	Mar. 01, 2017 USD ($)
Debt Instrument [Line Items]
Repayments of unsecured debt															$ 0	$ 155,375,000	$ 0
Loss on early extinguishment of debt															0	(4,271,000)	0
Repayment of unsecured line of credit															0	100,000,000	0
Unsecured notes payable, net															1,539,453,000	1,538,238,000
Unsecured line of credit, net															34,057,000	0
Unsecured line of credit
Debt Instrument [Line Items]
Maximum leverage ratio of revolving credit facility				60.00%
Maximum secured leverage ratio on revolving credit facility				40.00%
Minimum fixed charge coverage ratio covenant threshold							1.50
Minimum interest coverage ratio covenant threshold							175.00%
Maximum unsecured leverage ratio (in percentage)				60.00%
Maximum Recourse Indebtedness Of Total Asset Value				15.00%
Percentage annual distributions cannot exceed funds from operations														95.00%
Term Loan B & Term Loan C | Unsecured Debt | Subsequent Event
Debt Instrument [Line Items]
Face amount of debt	$ 225,000,000																	$ 150,000,000
Number of extensions available | extension	1
Extension term	12 months
Third Amended and Restated Credit Facility | Unsecured line of credit
Debt Instrument [Line Items]
Percentage annual distributions cannot exceed funds from operations				95.00%
American Assets Trust, L.P.
Debt Instrument [Line Items]
Repayments of unsecured debt															0	155,375,000	0
Loss on early extinguishment of debt															0	(4,271,000)	0
Repayment of unsecured line of credit															0	100,000,000	$ 0
Unsecured notes payable, net															1,539,453,000	1,538,238,000
Unsecured line of credit, net															34,057,000	0
American Assets Trust, L.P. | Secured notes payable
Debt Instrument [Line Items]
Principal Balance as of															75,000,000	111,000,000
American Assets Trust, L.P. | Unsecured line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Number of extensions available | extension														2
Extension term														6 months
American Assets Trust, L.P. | Unsecured line of credit | Revolving Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate				0.10%
American Assets Trust, L.P. | Unsecured line of credit | Revolving Credit Facility | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate				0.50%
American Assets Trust, L.P. | Unsecured line of credit | Revolving Credit Facility | Secured Overnight Financing Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate				1.05%
American Assets Trust, L.P. | Unsecured line of credit | Revolving Credit Facility | Secured Overnight Financing Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate				1.50%
American Assets Trust, L.P. | Unsecured Debt
Debt Instrument [Line Items]
Principal Balance as of															1,550,000,000	1,550,000,000
Unsecured notes payable, net															$ 1,539,453,000	1,538,238,000
American Assets Trust, L.P. | Unsecured Debt | Base Rate | Subsequent Event
Debt Instrument [Line Items]
Minimum base rate	0.00%
American Assets Trust, L.P. | Unsecured Debt | Federal Funds Rate | Subsequent Event
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
American Assets Trust, L.P. | Unsecured Debt | Secured Overnight Financing Rate | Subsequent Event
Debt Instrument [Line Items]
Basis spread on variable rate	1.00%
American Assets Trust, L.P. | Unsecured Debt | Secured Overnight Financing Rate | Subsequent Event | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.20%
American Assets Trust, L.P. | Unsecured Debt | Secured Overnight Financing Rate | Subsequent Event | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	1.90%
American Assets Trust, L.P. | 5.08% City Center Bellevue, October 2027 | Mortgages | Nonrecourse
Debt Instrument [Line Items]
Face amount of debt			$ 75,000,000
Debt instrument, term			5 years
Stated Interest Rate			5.08%
American Assets Trust, L.P. | 5.08% City Center Bellevue, October 2027 | Secured notes payable
Debt Instrument [Line Items]
Extinguishment of debt			$ 111,000,000
Stated Interest Rate															5.08%
Principal Balance as of															$ 75,000,000	0
American Assets Trust, L.P. | Senior unsecured notes, net
Debt Instrument [Line Items]
Stated Interest Rate					3.375%										3.375%
Note offering percent					0.98935
Weighted average yield of investment					3.502%
Proceeds from debt, net of issuance costs					$ 489,700,000
American Assets Trust, L.P. | Senior unsecured notes, net | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt					500,000,000
Stated Interest Rate															3.38%
Principal Balance as of															$ 500,000,000	500,000,000
American Assets Trust, L.P. | Senior Guaranteed Notes, Series A | Unsecured Debt
Debt Instrument [Line Items]
Repayments of unsecured debt					150,000,000
Loss on early extinguishment of debt					3,900,000
American Assets Trust, L.P. | Second Amended and Restated Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity							$ 450,000,000
Allowable additional borrowing capacity							$ 250,000,000
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit
Debt Instrument [Line Items]
Repayment of unsecured line of credit					$ 100,000,000
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Number of extensions available | extension							2
Extension term							6 months
Revolving credit facility borrowing limit, maximum borrowing capacity							$ 350,000,000
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate							1.00%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate							1.05%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate							1.50%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate							0.10%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate							0.50%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate							0.50%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured Debt
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity							$ 100,000,000
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate							1.30%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate							1.90%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured Debt | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate							0.30%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured Debt | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate							0.90%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured Debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate				0.50%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured Debt | Secured Overnight Financing Rate
Debt Instrument [Line Items]
Basis spread on variable rate				1.00%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Subsequent Event
Debt Instrument [Line Items]
Face amount of debt	$ 75,000,000																	150,000,000
Number of extensions available | extension	1
Extension term	12 months
American Assets Trust, L.P. | Term Loan B & Term Loan C | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate											0.70%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate											1.35%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt							$ 150,000,000
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Subsequent Event
Debt Instrument [Line Items]
Face amount of debt	$ 225,000,000																	$ 150,000,000
Number of extensions available | extension	1
Extension term	12 months
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate							1.20%				1.70%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate							1.70%				2.35%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Base Rate
Debt Instrument [Line Items]
Minimum base rate							0.00%				0.00%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate							0.70%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate							1.35%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Base Rate | Subsequent Event | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.20%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Base Rate | Subsequent Event | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	0.90%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate							0.50%				0.50%
American Assets Trust, L.P. | Term Loan B & Term Loan C | Unsecured Debt | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate							1.00%				1.00%
American Assets Trust, L.P. | Term Loan B
Debt Instrument [Line Items]
Face amount of debt											$ 100,000,000	$ 100,000,000
Debt instrument, term		2 years									7 years	7 years
American Assets Trust, L.P. | Term Loan B | Subsequent Event
Debt Instrument [Line Items]
Debt instrument, term	2 years
American Assets Trust, L.P. | Term Loan B | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt											$ 100,000,000
Principal Balance as of															100,000,000	100,000,000
American Assets Trust, L.P. | Term Loan C
Debt Instrument [Line Items]
Face amount of debt									$ 50,000,000	$ 50,000,000
Debt instrument, term									7 years	7 years
American Assets Trust, L.P. | Term Loan C | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt									$ 50,000,000
Principal Balance as of															$ 50,000,000	50,000,000
American Assets Trust, L.P. | Interest Rate Swap, Year One | Unsecured Debt | Subsequent Event
Debt Instrument [Line Items]
Fixed interest rate on derivative	5.47%
American Assets Trust, L.P. | Interest Rate Swap, Year Two | Unsecured Debt | Subsequent Event
Debt Instrument [Line Items]
Fixed interest rate on derivative	5.57%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Guaranteed Notes
Debt Instrument [Line Items]
Face amount of debt													$ 350,000,000
Partial debt repayment, minimum percentage of principal													5.00%
Full debt repayment percentage of principal plus a Make-Whole Amount													100.00%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Guaranteed Notes, Series A
Debt Instrument [Line Items]
Face amount of debt													$ 150,000,000
Stated Interest Rate													4.04%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Guaranteed Notes, Series B
Debt Instrument [Line Items]
Face amount of debt													$ 100,000,000
Stated Interest Rate													4.45%
American Assets Trust, L.P. | Note Purchase Agreement | Senior Guaranteed Notes, Series C
Debt Instrument [Line Items]
Face amount of debt													$ 100,000,000
Stated Interest Rate													4.50%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt																								$ 250,000,000
Stated Interest Rate															4.29%									4.29%
Principal Balance as of															$ 250,000,000	250,000,000
American Assets Trust, L.P. | Senior Guaranteed Notes, Series E | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt																							$ 100,000,000
Debt instrument, term								12 years
Stated Interest Rate															4.24%								4.24%
Principal Balance as of															$ 100,000,000	100,000,000
American Assets Trust, L.P. | Senior Guaranteed Notes, Series F | Unsecured Debt
Debt Instrument [Line Items]
Face amount of debt																						$ 100,000,000
Stated Interest Rate															3.78%							3.78%
Principal Balance as of															$ 100,000,000	100,000,000
American Assets Trust, L.P. | Senior Guaranteed Notes, Series G | Unsecured Debt
Debt Instrument [Line Items]
Stated Interest Rate															3.91%				3.91%
Principal Balance as of																150,000,000			$ 150,000,000
American Assets Trust, L.P. | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity														$ 350,000,000
Allowable additional borrowing capacity														$ 250,000,000
American Assets Trust, L.P. | Amended and Restated Credit Facility | Revolving Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate														0.35%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Revolving Credit Facility | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate														0.95%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity														$ 250,000,000
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate														1.35%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate														1.95%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured Debt
Debt Instrument [Line Items]
Number of extensions available | extension														3
Extension term														12 months
Revolving credit facility borrowing limit, maximum borrowing capacity														$ 100,000,000
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate														1.30%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate														1.90%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured Debt | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate														0.30%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured Debt | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate														0.90%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured Debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate														0.50%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured Debt | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate														1.00%
American Assets Trust, L.P. | Term Loan A
Debt Instrument [Line Items]
Face amount of debt		$ 225,000,000
Unsecured notes payable, net														$ 100,000,000
American Assets Trust, L.P. | Term Loan A | Subsequent Event
Debt Instrument [Line Items]
Face amount of debt	$ 225,000,000
American Assets Trust, L.P. | Term Loan A | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate						0.20%
American Assets Trust, L.P. | Term Loan A | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate						0.70%
American Assets Trust, L.P. | Term Loan A | Unsecured Debt
Debt Instrument [Line Items]
Number of extensions available | extension						3
Extension term						1 year
Principal Balance as of															$ 100,000,000	$ 100,000,000
American Assets Trust, L.P. | Term Loan A | Unsecured Debt | LIBOR | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate						1.20%
American Assets Trust, L.P. | Term Loan A | Unsecured Debt | LIBOR | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate						1.70%
American Assets Trust, L.P. | Term Loan A | Unsecured Debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate						0.50%
American Assets Trust, L.P. | Term Loan A | Unsecured Debt | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate						1.00%
American Assets Trust, L.P. | Third Amended and Restated Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity				$ 500,000,000
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate				0.20%
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate				0.70%
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Unsecured line of credit
Debt Instrument [Line Items]
Unsecured line of credit, net															36,000,000
Debt issuance costs, net, revolving credit facility															$ 1,900,000
Weighted average interest rate															4.38%
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity				$ 400,000,000
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Unsecured Debt
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
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Unsecured Debt | Base Rate
Debt Instrument [Line Items]
Minimum base rate				1.00%
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Unsecured Debt | Secured Overnight Financing Rate | Minimum
Debt Instrument [Line Items]
Basis spread on variable rate				1.20%
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Unsecured Debt | Secured Overnight Financing Rate | Maximum
Debt Instrument [Line Items]
Basis spread on variable rate				1.70%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan B
Debt Instrument [Line Items]
Fixed interest rate on derivative															3.15%						2.65%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan B | Unsecured Debt
Debt Instrument [Line Items]
Fixed interest rate on derivative											3.15%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan C
Debt Instrument [Line Items]
Fixed interest rate on derivative											3.14%				3.14%						2.64%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan A
Debt Instrument [Line Items]
Fixed interest rate on derivative															2.70%					4.13%