DERIVATIVE AND HEDGING (Details) - USD ($)							3 Months Ended
	Mar. 31, 2017	May. 02, 2016	Mar. 29, 2016	Mar. 23, 2016	Mar. 01, 2016	Jan. 29, 2016	Mar. 31, 2016	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Fair Value Liability							$ 5,654,000	$ 1,686,000
American Assets Trust, L.P. | Term Loan B
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Stated Maturity Date					Mar. 01, 2023
Face amount of debt					$ 100,000,000
Term of debt instrument					7 years
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
Face amount of debt							$ 100,000,000
American Assets Trust, L.P. | Term Loan | Scenario, Forecast
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Face amount of debt		$ 50,000,000
Term of debt instrument		7 years
American Assets Trust, L.P. | Unsecured term loans, net | Scenario, Forecast
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Term of debt instrument	10 years
American Assets Trust, L.P. | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative contract term			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%
Designated as Hedging Instrument | Cash Flow Hedging | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount			$ 150,000,000
Derivative fixed interest rate (in percent)			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 | Interest Rate Swap, 3/31/2027 | Wells Fargo Bank, N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Maturity Date							Mar. 31, 2027
Effective Date							Mar. 31, 2017
Designated as Hedging Instrument | Cash Flow Hedging | American Assets Trust, L.P. | Interest Rate Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative contract term				7 years		7 years
Notional Amount				$ 50,000,000		$ 100,000,000
Maturity Date			Mar. 31, 2027	Mar. 01, 2023		Mar. 01, 2023
Derivative fixed interest rate (in percent)				1.441%		1.4485%
Effective Date			Mar. 31, 2017	May 02, 2016		Mar. 01, 2016
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
Fair Value Liability							2,815,000
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
Fair Value Liability							1,365,000
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
Fair Value Liability							568,000
Designated as Hedging Instrument | Cash Flow Hedging | American Assets Trust, L.P. | Interest Rate Swap, 3/31/2027 | Wells Fargo Bank, N.A.
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional Amount							150,000,000
Fair Value Liability							$ 906,000