Debt Summary of Total Unsecured Notes Payable Outstanding (Details) $ in Thousands									12 Months Ended
		May 02, 2016	Apr. 07, 2016	Mar. 29, 2016	Mar. 23, 2016	Mar. 01, 2016	Jan. 29, 2016	Aug. 19, 2014	Dec. 31, 2016 USD ($) Extension_Option	Dec. 31, 2015 USD ($)	Jan. 09, 2014 USD ($)
Debt Instrument [Line Items]
Unsecured notes payable									$ 596,350	$ 446,613
American Assets Trust, L.P.
Debt Instrument [Line Items]
Unsecured notes payable									$ 596,350	446,613
American Assets Trust, L.P. | Interest Rate Swap
Debt Instrument [Line Items]
Fixed interest rate on derivative								2.1305%	3.08%
Term of derivative contract			10 years	10 years				7 years	7 years
American Assets Trust, L.P. | Forward Contracts
Debt Instrument [Line Items]
Term of derivative contract								1 month	1 month
Gain on derivatives									$ 1,600
Effective interest rate (percent)									3.88%
Term Loan A | American Assets Trust, L.P.
Debt Instrument [Line Items]
Unsecured notes payable											$ 100,000
Number of extensions available | Extension_Option									3
Extension term (in months)									12 months
Term Loan B | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Maturity Date						Mar. 01, 2023	Mar. 01, 2023
Term Loan B | American Assets Trust, L.P. | Interest Rate Swap
Debt Instrument [Line Items]
Fixed interest rate on derivative									3.15%
Term Loan C | American Assets Trust, L.P.
Debt Instrument [Line Items]
Stated Maturity Date		Mar. 01, 2023			Mar. 01, 2023
Term Loan C | American Assets Trust, L.P. | Interest Rate Swap
Debt Instrument [Line Items]
Fixed interest rate on derivative									3.14%
Unsecured debt | American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term debt									$ 600,000	450,000
Debt issuance costs, net									(3,650)	(3,387)
Unsecured notes payable									596,350	446,613
Debt issuance costs, accumulated amortization									4,317	2,999
Unsecured debt | Term Loan A | American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term debt									$ 100,000	100,000
Stated Maturity Date	[1]								Jan. 09, 2019
Unsecured debt | Senior Guaranteed Notes, Series A | American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term debt									$ 150,000	150,000
Stated Interest Rate	[2]								4.04%
Stated Maturity Date									Oct. 31, 2021
Unsecured debt | Senior Guaranteed Notes, Series B | American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term debt									$ 100,000	100,000
Stated Interest Rate									4.45%
Stated Maturity Date									Feb. 02, 2025
Unsecured debt | Senior Guaranteed Notes, Series C | American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term debt									$ 100,000	100,000
Stated Interest Rate									4.50%
Stated Maturity Date									Apr. 01, 2025
Unsecured debt | Term Loan B | American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term debt									$ 100,000	0
Stated Maturity Date									Mar. 01, 2023
Unsecured debt | Term Loan C | American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term debt									$ 50,000	$ 0
Stated Maturity Date									Mar. 01, 2023

[1] The Operating Partnership's Term Loan had an original maturity date of January 9, 2016 with an option to extend the Term Loan up to three times, with each such extension for a 12-month period, which we plan to exercise. The foregoing extension options are exercisable by the Operating Partnership subject to the satisfaction of certain conditions.

[2] The company 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 (see Note 8). 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.