DEBT - Summary of Total Unsecured Notes Payable Outstanding (Details) - American Assets Trust, L.P. $ in Thousands										6 Months Ended
		May 31, 2017	May 11, 2017 USD ($)	Apr. 25, 2017	Jan. 18, 2017 USD ($)	Apr. 07, 2016	Mar. 29, 2016	Sep. 19, 2014 USD ($)	Aug. 19, 2014	Jun. 30, 2017 USD ($) Extension_Option		Mar. 01, 2017	Dec. 31, 2016 USD ($)
Interest Rate Swap
Debt Instrument [Line Items]
Derivative contract term		7 years		10 years		10 years	10 years
Forward Contracts
Debt Instrument [Line Items]
Derivative contract term									7 years
Gain on derivative settlement			$ 700		$ 10,400			$ 1,600
Unsecured term loans, net
Debt Instrument [Line Items]
Long-term Debt, Principal Balance										$ 950,000			$ 600,000
Debt issuance costs, net										(5,184)			(3,650)
Total Debt Outstanding										944,816			596,350
Debt issuance costs, accumulated amortization										$ 5,068			4,317
Term Loan A
Debt Instrument [Line Items]
Debt extension options | Extension_Option										1
Term Loan A | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)										3.08%
Term Loan A | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Maturity Date	[1]									Jan. 09, 2019
Long-term Debt, Principal Balance										$ 100,000			100,000
Senior Guaranteed Notes, Series A | Forward Contracts
Debt Instrument [Line Items]
Effective rate of debt instrument (in percent)										3.88%
Senior Guaranteed Notes, Series A | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Interest Rate	[2]									4.04%
Stated Maturity Date										Oct. 31, 2021
Long-term Debt, Principal Balance										$ 150,000			150,000
Senior Guaranteed Notes, Series B | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Interest Rate										4.45%
Stated Maturity Date										Feb. 02, 2025
Long-term Debt, Principal Balance										$ 100,000			100,000
Senior Guaranteed Notes, Series C | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Interest Rate										4.50%
Stated Maturity Date										Apr. 01, 2025
Long-term Debt, Principal Balance										$ 100,000			100,000
Term Loan B | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)										3.15%
Term Loan B | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Maturity Date										Mar. 01, 2023
Long-term Debt, Principal Balance										$ 100,000			100,000
Term Loan C | Interest Rate Swap
Debt Instrument [Line Items]
Derivative fixed interest rate (in percent)										3.14%
Term Loan C | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Maturity Date										Mar. 01, 2023
Long-term Debt, Principal Balance										$ 50,000			50,000
Senior Guaranteed Notes, Series D | Forward Contracts
Debt Instrument [Line Items]
Effective rate of debt instrument (in percent)										3.87%
Senior Guaranteed Notes, Series D | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Interest Rate										4.29%	[3]	4.29%
Stated Maturity Date										Mar. 01, 2027
Long-term Debt, Principal Balance										$ 250,000			0
Senior Guaranteed Notes, Series E [Member] | Forward Contracts
Debt Instrument [Line Items]
Effective rate of debt instrument (in percent)										4.18%
Senior Guaranteed Notes, Series E [Member] | Unsecured term loans, net
Debt Instrument [Line Items]
Stated Interest Rate										4.24%	[4]	4.24%
Stated Maturity Date										May 23, 2029
Long-term Debt, Principal Balance										$ 100,000			$ 0

[1] The Operating Partnership has an option to extend the term loan up to one time, with such extension for a 12-month period. The foregoing extension option is exercisable by us subject to the satisfaction of certain conditions.

[2] The Operating Partnership entered into a one-month forward-starting seven-year swap contract on August 19, 2014, which was settled on September 19, 2014 at a gain of approximately $1.6 million. The forward-starting seven-year swap contract was deemed to be a highly effective cash flow hedge, accordingly, the effective interest rate is approximately 3.88% per annum.

[3] The Operating Partnership entered into forward-starting interest rate swap contracts on March 29, 2016 and April 7, 2016, which were settled on January 18, 2017 at a gain of approximately $10.4 million. The forward-starting interest swap rate contracts were deemed to be a highly effective cash flow hedge, accordingly, the effective interest rate is approximately 3.87% per annum.

[4] The Operating Partnerships entered into a treasury lock contract on April 25, 2017, which was settled on May 11, 2017 at a gain of approximately $0.7 million. The treasury lock contract was deemed to be a highly effective cash flow hedge, accordingly, the effective interest rate is approximately 4.18% per annum.