DEBT (Details)	Oct. 31, 2014 USD ($)	Jan. 09, 2014 USD ($) Extension_Option	Jun. 30, 2015 USD ($)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Unsecured line of credit			$ 30,000,000	$ 0
Unsecured line of credit | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Maximum leverage ratio of revolving credit facility (in percent)		60.00%
Maximum Unsecured Leverage Ratio		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		15.00%
Percentage limit on annual distributions in relation to funds from operations		95.00%
Unsecured line of credit | Amended and Restated Credit Facility | Base Rate
Debt Instrument [Line Items]
Debt Instrument, Spread on Variable Rate Basis, Two		0.50%
Debt Instrument, Spread on Variable Rate Basis, Three		1.00%
Unsecured term loan | Amended and Restated Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt Instrument, Description of Variable Rate Basis		LIBOR
Future Year Period Two | Unsecured line of credit
Debt Instrument [Line Items]
Minimum fixed charge coverage ratio on revolving credit facility (in percent)		1.5
Minimum Unsecured Interest Coverage Ratio		175.00%
Future Year Period Two | Unsecured line of credit | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Maximum secured leverage ratio on revolving credit facility (in percent)		40.00%
Future Year Period One | Unsecured line of credit | Amended and Restated Credit Facility
Debt Instrument [Line Items]
Maximum secured leverage ratio on revolving credit facility (in percent)		45.00%
American Assets Trust, L.P.
Debt Instrument [Line Items]
Unsecured line of credit			30,000,000	$ 0
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
Line of Credit Facility, Allowable Additional Borrowing Capacity		250,000,000
Unsecured line of credit		100,000,000
American Assets Trust, L.P. | Unsecured senior guaranteed notes | Note Purchase Agreement
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. | Senior Notes, Series A | Note Purchase Agreement
Debt Instrument [Line Items]
Face amount of debt	$ 150,000,000
Stated Interest Rate	4.00%
American Assets Trust, L.P. | Senior Notes, Series B | Note Purchase Agreement
Debt Instrument [Line Items]
Face amount of debt	$ 100,000,000
Stated Interest Rate	4.00%
American Assets Trust, L.P. | Senior Notes, Series C | Note Purchase Agreement
Debt Instrument [Line Items]
Face amount of debt	$ 100,000,000
Stated Interest Rate	5.00%
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
Debt Instrument, 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]
Debt Instrument, 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]
Debt Instrument, Description of Variable Rate Basis		base rate
Debt Instrument, Variable Rate Basis, One		prime rate
Debt Instrument, Variable Rate Basis, Two		federal funds rate
Debt Instrument, Variable Rate Basis, Three		Eurodollar
American Assets Trust, L.P. | Unsecured term loan | 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
Debt Instrument, Extension Term		12 months
Unsecured line of credit			$ 30,000,000
American Assets Trust, L.P. | Minimum | Amended and Restated Credit Facility | Base Rate | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.35%
American Assets Trust, L.P. | Minimum | Unsecured line of credit | Amended and Restated Credit Facility | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.35%
American Assets Trust, L.P. | Minimum | Unsecured term loan | Amended and Restated Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.30%
American Assets Trust, L.P. | Minimum | Unsecured term loan | Amended and Restated Credit Facility | Base Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.30%
American Assets Trust, L.P. | Maximum | Amended and Restated Credit Facility | Base Rate | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.95%
American Assets Trust, L.P. | Maximum | Unsecured line of credit | Amended and Restated Credit Facility | London Interbank Offered Rate (LIBOR) | Revolving Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.95%
American Assets Trust, L.P. | Maximum | Unsecured term loan | Amended and Restated Credit Facility | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		1.90%
American Assets Trust, L.P. | Maximum | Unsecured term loan | Amended and Restated Credit Facility | Base Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate		0.90%
American Assets Trust, L.P. | Interest Rate Swap | Cash Flow Hedging
Debt Instrument [Line Items]
Interest rate on derivative		3.08%