Quarterly Financial Information (Unaudited) Selected Quarterly Information (Details) - USD ($) $ / shares in Units, $ in Thousands	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
Quarterly Financial Information [Line Items]
Total revenue	$ 66,478	$ 67,343	$ 62,199	$ 63,980	$ 64,645	$ 65,318	$ 62,914	$ 62,180	$ 260,000	$ 255,057	$ 235,466
Operating income (loss)	22,526	23,036	17,726	20,381	20,407	21,441	19,373	19,880	83,669	81,101	71,906
Income (loss) from continuing operations									31,145	22,594	13,949
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 from continuing operations attributable to common stockholders-basic and diluted	$ 0.16	$ 0.15	$ 0.09	$ 0.11	$ 0.11	$ 0.11	$ 0.08	$ 0.08
Net income attributable to common stockholders-basic and diluted	$ 0.16	$ 0.15	$ 0.09	$ 0.11	$ 0.11	$ 0.11	$ 0.08	$ 0.08
American Assets Trust, L.P.
Quarterly Financial Information [Line Items]
Total revenue	$ 66,478	$ 67,343	$ 62,199	$ 63,980	$ 64,645	$ 65,318	$ 62,914	$ 62,180	260,000	255,057	235,466
Operating income (loss)	22,526	23,036	17,726	20,381	20,407	21,441	19,373	19,880	83,669	81,101	71,906
Income (loss) from continuing operations									31,145	22,594	13,949
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 from continuing operations attributable to common stockholders-basic and diluted	$ 0.16	$ 0.15	$ 0.09	$ 0.11	$ 0.11	$ 0.11	$ 0.08	$ 0.08
Net income attributable to common stockholders-basic and diluted	$ 0.16	$ 0.15	$ 0.09	$ 0.11	$ 0.11	$ 0.11	$ 0.08	$ 0.08
Net Income (Loss) Allocated to Limited Partners	$ (2,907)	$ (2,578)	$ (1,544)	$ (1,986)	$ (2,086)	$ (1,903)	$ (1,354)	$ (1,495)
Net Income (Loss) Allocated to General Partners	$ 7,024	$ 6,417	$ 3,713	$ 4,602	$ 4,682	$ 4,223	$ 3,077	$ 3,238

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[Line Items] for Quarterly Financial Information [Table]

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The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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Amount of income (loss) from a disposal group, net of income tax before extraordinary items allocable to noncontrolling interests. Includes, net of tax, income (loss) from operations during the phase-out period, gain (loss) on disposal, provision (or any reversals of earlier provisions) for loss on disposal, and adjustments of a prior period gain (loss) on disposal.

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Aggregate amount of net income allocated to general partners.

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