Debt (Details)											12 Months Ended
		May 02, 2016 USD ($)	Mar. 23, 2016	Mar. 01, 2016 USD ($)	Jan. 29, 2016	Oct. 31, 2014 USD ($)	Jan. 09, 2014 USD ($) Extension_Option	Sep. 07, 2012	Jan. 10, 2012	Mar. 07, 2011	Dec. 31, 2016 USD ($) Extension_Option	Dec. 31, 2015 USD ($)	Aug. 19, 2014	Jan. 19, 2011 USD ($)
Debt Instrument [Line Items]
Unsecured line of credit											$ 20,000,000	$ 30,000,000
Unsecured notes payable											596,350,000	446,613,000
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
Minimum interest coverage ratio covenant threshold							175.00%
Maximum unsecured leverage ratio (in percents)							60.00%
Minimum tangible net worth							$ 721,160,000.00
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%
Unsecured line of credit | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)							1.00%
Term Loan B | Unsecured debt | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on federal funds rate				0.50%
Term Loan B | Unsecured debt | Eurodollar
Debt Instrument [Line Items]
Basis spread on Eurodollar rate				1.00%
American Assets Trust, L.P.
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity														$ 250,000,000.0
Years, maximum maturities of securities										30 years
Year, extension on term of revolving credit facility									1 year
Percent of secured indebtedness of the company's secured total asset value								55.00%
Line of credit facility material acquisition								100
Unsecured line of credit											20,000,000	30,000,000
Unsecured notes payable											596,350,000	446,613,000
American Assets Trust, L.P. | Subject to meeting specified requirements and obtaining additional commitments
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity														$ 400,000,000.0
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 | 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 debt
Debt Instrument [Line Items]
Unsecured notes payable											$ 596,350,000	$ 446,613,000
American Assets Trust, L.P. | Term Loan A
Debt Instrument [Line Items]
Number of extensions available | Extension_Option											3
Extension term (in months)											12 months
Unsecured notes payable							$ 100,000,000
American Assets Trust, L.P. | Term Loan A | Unsecured debt
Debt Instrument [Line Items]
Stated Maturity Date	[1]										Jan. 09, 2019
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%
American Assets Trust, L.P. | Term Loan B | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)				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
American Assets Trust, L.P. | Term Loan B | Unsecured debt | LIBOR
Debt Instrument [Line Items]
Variable rate basis				LIBOR
American Assets Trust, L.P. | Term Loan B | Unsecured debt | Base Rate
Debt Instrument [Line Items]
Minimum base rate				0.00%
Prime rate				prime rate
Federal funds rate				federal funds rate
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)				1.70%
American Assets Trust, L.P. | Term Loan B | Unsecured debt | Maximum | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate (in percents)				2.35%
American Assets Trust, L.P. | Term Loan C
Debt Instrument [Line Items]
Number of year amortization schedule		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 | Unsecured debt
Debt Instrument [Line Items]
Face amount of debt		$ 50,000,000
Stated Maturity Date											Mar. 01, 2023
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
Debt Instrument [Line Items]
Unsecured line of credit											$ 20,000,000
Weighted average interest rate (in percent)											1.81%
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%
Interest Rate Swap | American Assets Trust, L.P.
Debt Instrument [Line Items]
Fixed interest rate on derivative											3.08%		2.1305%
Interest Rate Swap | American Assets Trust, L.P. | Term Loan B
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%

[1] The Operating Partnership's Term Loan had an original maturity date of January 9, 2016 with an option to extend the Term Loan up to three times, with each such extension for a 12-month period, which we plan to exercise. The foregoing extension options are exercisable by the Operating Partnership subject to the satisfaction of certain conditions.