Debt Summary of Total Unsecured Notes Payable Outstanding (Details) (USD $)	12 Months Ended		0 Months Ended
	Dec. 31, 2014 Extension_Option		Aug. 19, 2014	Dec. 31, 2013	Mar. 29, 2012
Debt Instrument [Line Items]
Unsecured notes payable	$ 250,000,000			$ 0
American Assets Trust, L.P.
Debt Instrument [Line Items]
Unsecured notes payable	250,000,000			0
Stated Interest Rate					3.94%
American Assets Trust, L.P. | Term Loan
Debt Instrument [Line Items]
Unsecured notes payable	100,000,000			0
Stated Maturity Date	Jan. 09, 2019	[1]
Number of extensions available	3
American Assets Trust, L.P. | Senior Guaranteed Notes, Series A
Debt Instrument [Line Items]
Unsecured notes payable	150,000,000			0
Stated Interest Rate	4.04%	[2]
Stated Maturity Date	Oct. 31, 2021
Interest Rate Swap
Debt Instrument [Line Items]
Fixed interest rate on derivative			2.1305%
Term of derivative contract			7 years
Interest Rate Swap | American Assets Trust, L.P.
Debt Instrument [Line Items]
Fixed interest rate on derivative	3.08%
Forward Contracts | American Assets Trust, L.P.
Debt Instrument [Line Items]
Term of derivative contract	1 month
Gain on derivatives	$ 1,600,000
Effective interest rate (percent)	3.88%

[1] The Operating Partnership has an option to extend the term loan up to three times, with each such extension for a 12-month period. 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 9). 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.