Equity of American Assets Trust, Inc. Summary of Income Tax Status of Dividends Per Share Paid (Details) - $ / shares	3 Months Ended												12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Equity [Abstract]
Ordinary income (in USD per share)													$ 0.72	$ 0.61	$ 0.83
Capital gain (in USD per share)													0.04	0.00	0.00
Return of capital (in USD per share)													0.19	0.28	0.02
Total (in USD per share)	$ 0.25	$ 0.2325	$ 0.2325	$ 0.2325	$ 0.2325	$ 0.22	$ 0.22	$ 0.22	$ 0.22	$ 0.21	$ 0.21	$ 0.2100	$ 0.95	$ 0.89	$ 0.85
Ordinary income													75.90%	68.90%	97.60%
Capital gain													4.40%	0.00%	0.00%
Return of capital													19.70%	31.10%	2.40%
Total													100.00%	100.00%	100.00%