DERIVATIVE AND HEDGING ACTIVITIES (Details) - USD ($)						3 Months Ended
	Mar. 31, 2017	Mar. 01, 2017	Jan. 18, 2017	Apr. 07, 2016	Mar. 29, 2016	Mar. 31, 2017
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Stated Maturity Date		Mar. 01, 2027
Term of debt instrument	10 years
American Assets Trust, L.P. | Senior Guaranteed Notes, Series D | Unsecured term loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Stated Maturity Date						Mar. 01, 2027
Face amount of debt		$ 250,000,000
American Assets Trust, L.P. | Term Loan B | Unsecured term loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Stated Maturity Date						Mar. 01, 2023
American Assets Trust, L.P. | Term Loan C | Unsecured term loans, net
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Stated Maturity Date						Mar. 01, 2023
American Assets Trust, L.P. | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative contract term				10 years	10 years
American Assets Trust, L.P. | Interest Rate Swap | Term Loan B
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative fixed interest rate (in percent)	3.15%					3.15%
American Assets Trust, L.P. | Interest Rate Swap | Term Loan C
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative fixed interest rate (in percent)	3.14%					3.14%
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount				$ 100,000,000	$ 150,000,000
Derivative fixed interest rate (in percent)				1.748%	1.88%
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap, 1/9/2019 | Bank of America, N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Maturity Date						Jan. 09, 2019
Effective Date						Jan. 09, 2014
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap, 3/1/2023 | U.S. Bank N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Maturity Date						Mar. 01, 2023
Effective Date						Mar. 01, 2016
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap, 3/1/2023 | Wells Fargo Bank, N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Maturity Date						Mar. 01, 2023
Effective Date						May 02, 2016
Designated as Hedging Instrument | Cash Flow Hedging | American Assets Trust, L.P. | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Maturity Date				Mar. 31, 2027	Mar. 31, 2027
Effective Date				Mar. 31, 2017	Mar. 31, 2017
Gain recognized in other comprehensive income (loss)			$ 10,400,000
Designated as Hedging Instrument | Cash Flow Hedging | American Assets Trust, L.P. | Interest Rate Swap, 1/9/2019 | Bank of America, N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	$ 100,000,000					$ 100,000,000
Interest rate swap liability	(649,000)					(649,000)
Designated as Hedging Instrument | Cash Flow Hedging | American Assets Trust, L.P. | Interest Rate Swap, 3/1/2023 | U.S. Bank N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	100,000,000					100,000,000
Interest rate swap asset	3,029,000					3,029,000
Designated as Hedging Instrument | Cash Flow Hedging | American Assets Trust, L.P. | Interest Rate Swap, 3/1/2023 | Wells Fargo Bank, N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount	50,000,000					50,000,000
Interest rate swap asset	$ 1,556,000					$ 1,556,000