DEBT (Details)					9 Months Ended
	May 02, 2016 USD ($)	Mar. 01, 2016 USD ($)	Jan. 29, 2016	Jan. 09, 2014 USD ($) Extension_Option	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Unsecured line of credit					$ 0	$ 30,000,000
Unsecured term loans, net | Term Loan B | Base Rate
Debt Instrument [Line Items]
Basis spread on federal funds rate		0.50%
Basis spread on Eurodollar rate		1.00%
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 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	$ 30,000,000
American Assets Trust, L.P. | Term Loan B
Debt Instrument [Line Items]
Term of debt instrument		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		0.70%
American Assets Trust, L.P. | Term Loan B | Maximum | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate		1.35%
American Assets Trust, L.P. | Term Loan B | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)					3.15%
American Assets Trust, L.P. | Term Loan C
Debt Instrument [Line Items]
Term of debt instrument	7 years
Face amount of debt	$ 50,000,000
Stated Maturity Date	Mar. 01, 2023
American Assets Trust, L.P. | Term Loan C | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)					3.14%
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. | Unsecured term loans, net | Term Loan B
Debt Instrument [Line Items]
Face amount of debt		$ 100,000,000
Stated Maturity Date					Mar. 01, 2023
American Assets Trust, L.P. | Unsecured term loans, net | Term Loan B | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Description of variable rate basis		LIBOR
American Assets Trust, L.P. | Unsecured term loans, net | Term Loan B | Base Rate
Debt Instrument [Line Items]
0% rate		0.00%
Prime rate		prime rate
Federal funds rate		federal funds rate
Eurodollar rate		Eurodollar
American Assets Trust, L.P. | Unsecured term loans, net | Term Loan B | Minimum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		1.70%
American Assets Trust, L.P. | Unsecured term loans, net | Term Loan B | Maximum | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		2.35%
American Assets Trust, L.P. | Unsecured term loans, net | Term Loan C
Debt Instrument [Line Items]
Face amount of debt	$ 50,000,000
Stated Maturity Date					Mar. 01, 2023
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 line of credit | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Unsecured line of credit					$ 0
Weighted average interest rate					1.77%
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%