DEBT (Details)			3 Months Ended
	Mar. 01, 2016 USD ($)	Jan. 09, 2014 USD ($) Extension_Option	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Unsecured line of credit			$ 20,000,000	$ 30,000,000
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%
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
American Assets Trust, L.P.
Debt Instrument [Line Items]
Unsecured line of credit			$ 20,000,000	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
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. | 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 | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate		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		0.95%
American Assets Trust, L.P. | Interest Rate Swap | Term Loan B
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)			3.15%
American Assets Trust, L.P. | Secured notes payable, net
Debt Instrument [Line Items]
Long-term Debt, Principal Balance			$ 499,063,000	584,002,000
Debt issuance costs, accumulated amortization			1,291,000	1,649,000
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Unsecured line of credit			$ 20,000,000
Debt Instrument, Interest Rate During Period			1.75%
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 | 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 | Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Description of variable rate basis		LIBOR
American Assets Trust, L.P. | Unsecured line of credit | Amended and Restated Credit Facility | Minimum | Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
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 | Revolving Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate		1.95%
American Assets Trust, L.P. | Unsecured term loans, net
Debt Instrument [Line Items]
Long-term Debt, Principal Balance			$ 550,000,000	450,000,000
Debt issuance costs, accumulated amortization			3,300,000	2,999,000
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
Long-term Debt, Principal Balance			$ 100,000,000	$ 0
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]
Prime rate	prime rate
Federal funds rate	federal funds rate
Eurodollar rate	Eurodollar
0% rate	0
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 | 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%