DEBT (Details)							3 Months Ended
		Mar. 31, 2017 USD ($) Extension_Option		Mar. 01, 2017 USD ($)	Mar. 01, 2016	Jan. 09, 2014 USD ($) Extension_Option	Mar. 31, 2017 USD ($) Extension_Option		Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)
Debt Instrument [Line Items]
Unsecured line of credit		$ 0					$ 0		$ 20,000,000
Unsecured term loans, net | Amended and Restated Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Description of variable rate basis						LIBOR
Unsecured term loans, net | Term Loan A | Base Rate
Debt Instrument [Line Items]
Basis spread on federal funds rate					0.50%
Basis spread on Eurodollar rate					1.00%
Unsecured line of credit | Amended and Restated Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on federal funds rate						0.50%
Basis spread on Eurodollar rate						1.00%
American Assets Trust, L.P.
Debt Instrument [Line Items]
Unsecured line of credit		$ 0					$ 0		$ 20,000,000
American Assets Trust, L.P. | Term Loan C | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)		3.14%					3.14%
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D
Debt Instrument [Line Items]
Term of debt instrument		10 years
Stated Maturity Date				Mar. 01, 2027
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
Additional borrowing capacity						$ 250,000,000
American Assets Trust, L.P. | Amended and Restated Credit Facility | Minimum | Base Rate | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate						0.35%
American Assets Trust, L.P. | Amended and Restated Credit Facility | Maximum | Base Rate | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate						0.95%
American Assets Trust, L.P. | Term Loan A
Debt Instrument [Line Items]
Debt extension options | Extension_Option		1					1
American Assets Trust, L.P. | Term Loan A | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)		3.08%					3.08%
American Assets Trust, L.P. | Unsecured term loans, net | Term Loan C
Debt Instrument [Line Items]
Stated Maturity Date							Mar. 01, 2023
American Assets Trust, L.P. | Unsecured term loans, net | Senior Guaranteed Notes, Series D
Debt Instrument [Line Items]
Face amount of debt				$ 250,000,000
Stated Interest Rate		4.29%	[1]	4.29%			4.29%	[1]
Stated Maturity Date							Mar. 01, 2027
Debt Instrument, Partial Repayment, Minimum Percentage of Principal				5.00%
Debt Instrument, Prepayment, Percentage of Principal Plus a Stated Amount				100.00%
American Assets Trust, L.P. | Unsecured term loans, net | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity						$ 100,000,000
Debt extension options | Extension_Option						3
Extension term						12 months
American Assets Trust, L.P. | Unsecured term loans, net | Amended and Restated Credit Facility | Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate						1.30%
American Assets Trust, L.P. | Unsecured term loans, net | Amended and Restated Credit Facility | Minimum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate						0.30%
American Assets Trust, L.P. | Unsecured term loans, net | Amended and Restated Credit Facility | Maximum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate						1.90%
American Assets Trust, L.P. | Unsecured term loans, net | Amended and Restated Credit Facility | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate						0.90%
American Assets Trust, L.P. | Unsecured term loans, net | Term Loan A
Debt Instrument [Line Items]
Stated Maturity Date	[2]						Jan. 09, 2019
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Unsecured line of credit										$ 0
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Revolving credit facility borrowing limit, maximum borrowing capacity						$ 250,000,000
Debt extension options | Extension_Option						2
Extension term						6 months
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Debt Instrument [Line Items]
Description of variable rate basis						LIBOR
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility | Base Rate
Debt Instrument [Line Items]
Description of variable rate basis						base rate
Prime rate						prime rate
Federal funds rate						federal funds rate
Eurodollar rate						Eurodollar
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility | Minimum | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate						1.35%
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility | Maximum | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Debt Instrument [Line Items]
Basis spread on variable rate						1.95%

[1] The Operating Partnership entered into forward-starting interest rate swap contracts on March 29, 2016 and April 7, 2016, which were settled on January 18, 2017 at a gain of approximately $10.4 million. The forward-starting interest swap rate contracts were deemed to be a highly effective cash flow hedge, accordingly, the effective interest rate in accordance with GAAP is approximately 3.87% per annum.

[2] The Operating Partnership has an option to extend the term loan up to one time, with such extension for a 12-month period. The foregoing extension option is exercisable by us subject to the satisfaction of certain conditions.