Equity of American Assets Trust, Inc. Restricted Common Stock Issued (Details) - Restricted Stock - $ / shares		Dec. 06, 2018		Jun. 12, 2018	[1]	Dec. 15, 2017		Jun. 13, 2017	[1]	Dec. 01, 2016		Jun. 14, 2016	[1]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		33.30%								33.30%
Granted, Weighted Average Grant Date Fair Value (in USD per share)				$ 37.58		$ 27.27		$ 40.99				$ 40.81
Granted, Shares		199,790	[2]	5,320		145,218	[2]	4,880		143,210	[3]	4,900
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Weighted Average Grant Date Fair Value (in USD per share)	[2]	$ 25.68								$ 28.24
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, Weighted Average Grant Date Fair Value (in USD per share)	[2]	$ 28.18								$ 35.71

[1] Restricted common stock issued to members of the company's non-employee directors. These awards of restricted stock will vest subject to the director's continued service on the Board of Directors on the earlier of (i) the one year anniversary of the date of grant or (ii) the date of the next annual meeting of our stockholders, if such non-employee director continues his or her service on the Board of Directors until the next annual meeting of stockholders, but not thereafter, pursuant to our independent director compensation policy.

[2] Restricted common stock issued to certain of the company's senior management and other employees, which are subject to pre-defined market specific performance criteria based vesting. Shares of restricted stock may vest based on performance calculations determined as of November 30, 2018, subject to the employee's continued employment on that date.

[3] Restricted common stock issued to certain of the company's senior management and other employees, which are subject to pre-defined market specific performance criteria based vesting. Up to one-third of the shares of restricted stock may vest based on performance calculations determined as of November 30, 2017, 2018 and 2019, subject to the employee's continued employment on those dates.