Debt (Details)																			12 Months Ended
	Jan. 14, 2022 USD ($)	Jan. 05, 2022 USD ($) Extension_Option	Jan. 26, 2021 USD ($)	Aug. 11, 2020 USD ($)	Jun. 20, 2019 USD ($)	Jan. 09, 2019 Extension_Option	Jan. 09, 2018 USD ($) Extension_Option	May 31, 2017 USD ($)	Apr. 25, 2017 USD ($)	Mar. 31, 2017	May 02, 2016 USD ($)	Apr. 07, 2016 USD ($)	Mar. 29, 2016 USD ($)	Mar. 23, 2016 USD ($)	Mar. 01, 2016 USD ($)	Jan. 29, 2016 USD ($)	Oct. 31, 2014 USD ($)	Jan. 09, 2014 USD ($) Extension_Option	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 30, 2019 USD ($)	Dec. 31, 2018	Jul. 19, 2017 USD ($)	May 23, 2017 USD ($)	Mar. 01, 2017 USD ($)
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period																			1.14%
Unsecured line of credit, net																			$ 0	$ 99,151,000
Unsecured notes payable, net																			1,538,238,000	1,196,677,000
Repayments of Unsecured Debt																			155,375,000	0	$ 0
Loss on early extinguishment of debt																			(4,271,000)	0	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							1.5											1.5
Minimum interest coverage ratio covenant threshold							175.00%											175.00%
Maximum unsecured leverage ratio (in percents)							60.00%
Minimum tangible net worth																		$ 721,160,000
Percent of net proceeds of any additional equity issuances in relation to net proceeds as of Offering																		75.00%
Maximum recourse indebtedness of total asset value (in percents)							15.00%
Percentage annual distributions cannot exceed funds from operations																		95.00%
Unsecured line of credit | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.50%											0.50%
Unsecured line of credit | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		1.00%
Term Loan A | Unsecured debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on federal funds rate						0.50%
Term Loan A | Unsecured debt | Federal Funds Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on federal funds rate		0.50%
Term Loan A | Unsecured debt | Eurodollar
Debt Instrument [Line Items]
Basis spread on Eurodollar rate						1.00%
Term Loan A | Unsecured debt | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on Eurodollar rate		1.00%
Term Loan A | Unsecured debt | Minimum | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Spread on Variable Rate Basis, Four		0.20%
Term Loan A | Unsecured debt | Maximum | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Spread on Variable Rate Basis, Four		0.70%
Term Loan B | Unsecured debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on federal funds rate							0.50%								0.50%
Term Loan B | Unsecured debt | Eurodollar
Debt Instrument [Line Items]
Basis spread on Eurodollar rate							1.00%								1.00%
Term Loan C | Unsecured debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on federal funds rate							0.50%
Term Loan C | Unsecured debt | Eurodollar
Debt Instrument [Line Items]
Basis spread on Eurodollar rate							1.00%
Second Amended and Restated Credit Facility | Unsecured line of credit
Debt Instrument [Line Items]
Percentage annual distributions cannot exceed funds from operations							95.00%
Second Amended and Restated Credit Facility | Unsecured line of credit | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.00%
Unsecured line of credit | Unsecured debt | Federal Funds Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on federal funds rate		0.50%
Unsecured line of credit | Unsecured debt | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on Eurodollar rate		1.00%
Unsecured line of credit | Unsecured debt | Minimum | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Spread on Variable Rate Basis, Four		0.10%
Unsecured line of credit | Unsecured debt | Maximum | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Spread on Variable Rate Basis, Four		0.50%
American Assets Trust, L.P.
Debt Instrument [Line Items]
Unsecured line of credit, net																			0	99,151,000
Unsecured notes payable, net																			1,538,238,000	1,196,677,000
Repayments of Unsecured Debt																			155,375,000	0	0
Loss on early extinguishment of debt																			(4,271,000)	0	$ 0
American Assets Trust, L.P. | Unsecured line of credit | Base Rate
Debt Instrument [Line Items]
Variable rate basis																		base rate
American Assets Trust, L.P. | Unsecured line of credit | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Variable rate basis		SOFR
American Assets Trust, L.P. | Unsecured line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Number of extensions available | Extension_Option																		2
Extension term (in months)																		6 months
American Assets Trust, L.P. | Unsecured line of credit | Minimum | Revolving Credit Facility | LIBOR | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.05%
American Assets Trust, L.P. | Unsecured line of credit | Minimum | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.10%
American Assets Trust, L.P. | Unsecured line of credit | Maximum | Revolving Credit Facility | LIBOR | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.50%
American Assets Trust, L.P. | Unsecured line of credit | Maximum | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.50%
American Assets Trust, L.P. | Unsecured debt
Debt Instrument [Line Items]
Long-term Debt, Principal Balance																			1,550,000,000	1,200,000,000
Unsecured notes payable, net																			$ 1,538,238,000	1,196,677,000
American Assets Trust, L.P. | Term Loan A
Debt Instrument [Line Items]
Unsecured notes payable, net																		$ 100,000,000
American Assets Trust, L.P. | Term Loan A | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)						0.20%
American Assets Trust, L.P. | Term Loan A | Minimum | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		0.20%
American Assets Trust, L.P. | Term Loan A | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)						0.70%
American Assets Trust, L.P. | Term Loan A | Maximum | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		0.70%
American Assets Trust, L.P. | Term Loan A | Unsecured debt
Debt Instrument [Line Items]
Stated Maturity Date																			Jan. 09, 2022
Long-term Debt, Principal Balance																			$ 100,000,000	100,000,000
Number of extensions available | Extension_Option						3
Extension term (in months)						1 year
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Subsequent Event [Member]
Debt Instrument [Line Items]
Number of extensions available | Extension_Option		2
Extension term (in months)		6 months
American Assets Trust, L.P. | Term Loan A | Unsecured debt | LIBOR
Debt Instrument [Line Items]
Variable rate basis						LIBOR
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Base Rate
Debt Instrument [Line Items]
Prime rate						prime rate
Federal funds rate						federal funds rate
Eurodollar						Eurodollar
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Variable Rate Basis, Five		0.00%
Minimum base rate		1.00%
Prime rate		prime rate
Federal funds rate		federal funds rate
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Variable rate basis		SOFR
Eurodollar		SOFR
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Minimum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)						1.20%
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Minimum | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.20%
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Maximum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)						1.70%
American Assets Trust, L.P. | Term Loan A | Unsecured debt | Maximum | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.70%
American Assets Trust, L.P. | Term Loan B
Debt Instrument [Line Items]
Number of year amortization schedule															7 years
Face amount of debt															$ 100,000,000
Stated Maturity Date															Mar. 01, 2023	Mar. 01, 2023
American Assets Trust, L.P. | Term Loan B | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.70%								0.70%
American Assets Trust, L.P. | Term Loan B | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.35%								1.35%
American Assets Trust, L.P. | Term Loan B | Unsecured debt
Debt Instrument [Line Items]
Face amount of debt															$ 100,000,000
Stated Maturity Date																			Mar. 01, 2023
Long-term Debt, Principal Balance																			$ 100,000,000	100,000,000
American Assets Trust, L.P. | Term Loan B | Unsecured debt | LIBOR
Debt Instrument [Line Items]
Variable rate basis							LIBOR								LIBOR
American Assets Trust, L.P. | Term Loan B | Unsecured debt | Base Rate
Debt Instrument [Line Items]
Minimum base rate							0.00%								0.00%
Prime rate							prime rate								prime rate
Federal funds rate							federal funds rate								federal funds rate
Eurodollar							Eurodollar								Eurodollar
American Assets Trust, L.P. | Term Loan B | Unsecured debt | Minimum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.20%								1.70%
American Assets Trust, L.P. | Term Loan B | Unsecured debt | Maximum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.70%								2.35%
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 C
Debt Instrument [Line Items]
Number of year amortization schedule							7 years				7 years
Face amount of debt											$ 50,000,000
Stated Maturity Date											Mar. 01, 2023			Mar. 01, 2023
American Assets Trust, L.P. | Term Loan C | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.70%				0.70%
American Assets Trust, L.P. | Term Loan C | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.35%				1.35%
American Assets Trust, L.P. | Term Loan C | Unsecured debt
Debt Instrument [Line Items]
Face amount of debt											$ 50,000,000
Stated Maturity Date																			Mar. 01, 2023
Long-term Debt, Principal Balance																			$ 50,000,000	50,000,000
American Assets Trust, L.P. | Term Loan C | Unsecured debt | LIBOR
Debt Instrument [Line Items]
Variable rate basis							LIBOR				LIBOR
American Assets Trust, L.P. | Term Loan C | Unsecured debt | Base Rate
Debt Instrument [Line Items]
Minimum base rate							0.00%				0.00%
Prime rate							prime rate				prime rate
Federal funds rate							federal funds rate				federal funds rate
Eurodollar							Eurodollar				Eurodollar
American Assets Trust, L.P. | Term Loan C | Unsecured debt | Minimum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.20%				1.70%
American Assets Trust, L.P. | Term Loan C | Unsecured debt | Maximum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.70%				2.35%
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 (in percent)																	5.00%
Full debt repayment percentage of principal plus a Make-Whole Amount (in percent)																	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. | 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 | Minimum | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		0.35%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Maximum | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		0.95%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured line of credit | Base Rate
Debt Instrument [Line Items]
Prime rate																		prime rate
Federal funds rate																		federal funds rate
Eurodollar																		Eurodollar
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
Debt Instrument [Line Items]
Variable rate basis																		LIBOR
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured line of credit | Minimum | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		1.35%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured line of credit | Maximum | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		1.95%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured debt
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity																		$ 100,000,000
Number of extensions available | Extension_Option																		3
Extension term (in months)																		12 months
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured debt | Minimum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		1.30%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured debt | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		0.30%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured debt | Maximum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		1.90%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Unsecured debt | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)																		0.90%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D | Unsecured debt
Debt Instrument [Line Items]
Face amount of debt																										$ 250,000,000
Stated Maturity Date																			Mar. 01, 2027
Stated Interest Rate																			4.29%							4.29%
Long-term Debt, Principal Balance																			$ 250,000,000	250,000,000
American Assets Trust, L.P. | Senior Guaranteed Notes, Series E | Unsecured debt
Debt Instrument [Line Items]
Number of year amortization schedule									12 years
Face amount of debt																									$ 100,000,000
Stated Maturity Date																			May 23, 2029
Stated Interest Rate																			4.24%						4.24%
Long-term Debt, Principal Balance																			$ 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 Maturity Date																			Jul. 19, 2024
Stated Interest Rate																			3.78%					3.78%
Long-term Debt, Principal Balance																			$ 100,000,000	100,000,000
American Assets Trust, L.P. | Senior Guaranteed Notes, Series G [Member] | Unsecured debt
Debt Instrument [Line Items]
Stated Interest Rate																			3.91%			3.91%
Long-term Debt, Principal Balance																				150,000,000		$ 150,000,000
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]
Unsecured line of credit, net																			$ 0
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Base Rate
Debt Instrument [Line Items]
Prime rate							prime rate
Federal funds rate							federal funds rate
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity							$ 350,000,000
Number of extensions available | Extension_Option							2
Extension term (in months)							6 months
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Variable rate basis							LIBOR
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Minimum | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.05%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Minimum | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.10%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Maximum | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.50%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured line of credit | Maximum | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							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 | Minimum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.30%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured debt | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.30%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured debt | Maximum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.90%
American Assets Trust, L.P. | Second Amended and Restated Credit Facility | Unsecured debt | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							0.90%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series A | Unsecured debt
Debt Instrument [Line Items]
Stated Maturity Date																			Oct. 31, 2021
Stated Interest Rate																			4.04%
Long-term Debt, Principal Balance																			$ 0	150,000,000
Repayments of Unsecured Debt			$ 150,000,000
Loss on early extinguishment of debt			$ 3,900,000
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 debt
Debt Instrument [Line Items]
Face amount of debt			$ 500,000,000
Stated Maturity Date																			Feb. 01, 2031
Stated Interest Rate																			3.38%
Long-term Debt, Principal Balance																			$ 500,000,000	$ 0
American Assets Trust, L.P. | Unsecured debt
Debt Instrument [Line Items]
Number of year amortization schedule										10 years
American Assets Trust, L.P. | Unsecured line of credit | Unsecured debt | Base Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Debt Instrument, Variable Rate Basis, Five		0.00%
Minimum base rate		1.00%
Prime rate		prime rate
Federal funds rate		federal funds rate
American Assets Trust, L.P. | Unsecured line of credit | Unsecured debt | Minimum | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.05%
American Assets Trust, L.P. | Unsecured line of credit | Unsecured debt | Maximum | Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subsequent Event [Member]
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)		1.50%
American Assets Trust, L.P. | Third Amended and Restated Credit Facility | Subsequent Event [Member]
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 | Unsecured line of credit | Revolving Credit Facility | Subsequent Event [Member]
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 | Subsequent Event [Member]
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity		$ 100,000,000
Interest Rate Swap | Designated as Hedging Instrument | Cash Flow Hedging
Debt Instrument [Line Items]
Fixed interest rate on derivative												1.748%	1.88%
Notional amount												$ 100,000,000	$ 150,000,000
Interest Rate Swap | American Assets Trust, L.P. | Designated as Hedging Instrument | Cash Flow Hedging
Debt Instrument [Line Items]
Fixed interest rate on derivative														1.441%		1.4485%			4.13%
Notional amount														$ 50,000,000		$ 100,000,000			$ 100,000,000
Maturity date												Mar. 31, 2027	Mar. 31, 2027	Mar. 01, 2023		Mar. 01, 2023
Interest Rate Swap | American Assets Trust, L.P. | Term Loan A
Debt Instrument [Line Items]
Fixed interest rate on derivative																			4.13%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan A | Subsequent Event [Member]
Debt Instrument [Line Items]
Fixed interest rate on derivative	2.80%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan B
Debt Instrument [Line Items]
Fixed interest rate on derivative															3.15%				2.65%				3.15%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan C
Debt Instrument [Line Items]
Fixed interest rate on derivative															3.14%				2.64%				3.14%
Treasury Lock | American Assets Trust, L.P. | Designated as Hedging Instrument | Cash Flow Hedging
Debt Instrument [Line Items]
Fixed interest rate on derivative								2.064%	2.313%
Notional amount								$ 100,000,000	$ 100,000,000
Maturity date								Jul. 26, 2017
Treasury Lock | American Assets Trust, L.P. | Wells Fargo Bank, N.A. | Not Designated as Hedging Instrument [Member]
Debt Instrument [Line Items]
Fixed interest rate on derivative				0.7115%
Notional amount				$ 200,000,000
Maturity date				Nov. 12, 2020
Treasury Lock | American Assets Trust, L.P. | Wells Fargo Bank, N.A. | Designated as Hedging Instrument | Cash Flow Hedging
Debt Instrument [Line Items]
Fixed interest rate on derivative					1.9925%
Notional amount					$ 100,000,000
Maturity date					Jul. 31, 2019
Treasury Lock | American Assets Trust, L.P. | Subsequent Event [Member] | Wells Fargo Bank, N.A. | Not Designated as Hedging Instrument [Member]
Debt Instrument [Line Items]
Notional amount	$ 50,000,000
Treasury Lock | American Assets Trust, L.P. | Subsequent Event [Member] | Wells Fargo Bank, N.A. | Designated as Hedging Instrument | Cash Flow Hedging
Debt Instrument [Line Items]
Fixed interest rate on derivative	2.80%
Maturity date	Jan. 05, 2027