Segment Reporting Reconciliation of Segment Profit to Net Income Attributable to Stockholders (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	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, 2014	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting [Abstract]
Gross Profit									$ 168,769	$ 165,071	$ 149,352
General and administrative									(18,532)	(17,195)	(15,593)
Depreciation and amortization									(66,568)	(66,775)	(61,853)
Interest expense									(52,965)	(58,020)	(57,328)
Other income (expense), net									441	(487)	(629)
Income from continuing operations									31,145	22,594	13,949
Discontinued operations
Income from discontinued operations									0	0	932
Gain on sale of real estate property									0	0	36,720
Results from discontinued operations									0	0	37,652
Net income	10,046	9,090	5,351	6,658	6,907	6,258	4,564	4,865	31,145	22,594	51,601
Net income attributable to restricted shares	(115)	(95)	(94)	(70)	(139)	(132)	(133)	(132)	(374)	(536)	(529)
Net income attributable to unitholders in the Operating Partnership	(2,907)	(2,578)	(1,544)	(1,986)	(2,086)	(1,903)	(1,354)	(1,495)	(9,015)	(6,838)	(16,134)
Net income attributable to American Assets Trust, Inc. stockholders	$ 7,024	$ 6,417	$ 3,713	$ 4,602	$ 4,682	$ 4,223	$ 3,077	$ 3,238	$ 21,756	$ 15,220	$ 34,938