Reconciliation of Segment Profit to Net Income Attributable to Stockholders (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Total segments' profit									$ 149,352	$ 125,906	$ 85,540
General and administrative									(15,593)	(13,627)	(8,699)
Depreciation and amortization									(61,853)	(55,936)	(34,419)
Interest expense									(57,328)	(54,580)	(43,251)
Early extinguishment of debt										(25,867)
Loan transfer and consent fees										(8,808)
Gain on acquisition										46,371	4,297
Other income (expense), net									(629)	212	(1,846)
Income from continuing operations	4,822	3,968	2,396	2,763	560	(59)	(172)	13,342	13,949	13,671	1,622
Discontinued operations
Income from discontinued operations									932	1,672	552
Gain on sale of real estate property									36,720	3,981
Results from discontinued operations	36,999	317	228	108	95	4,677	627	254	37,652	5,653	552
Net income	41,821	4,285	2,624	2,871	655	4,618	455	13,596	51,601	19,324	2,174
Net income attributable to restricted shares	(133)	(133)	(131)	(132)	(132)	(132)	(132)	(86)	(529)	(482)
Net loss attributable to Predecessor's noncontrolling interests in consolidated real estate entities								(2,458)		2,458	2,205
Net income attributable to Predecessor's controlled owners' equity								(16,995)		(16,995)	(4,379)
Net income attributable to unitholders in the Operating Partnership	13,111	1,335	804	883	179	1,434	104	(329)	(16,133)	(1,388)
Net income attributable to American Assets Trust, Inc. stockholders	$ 28,577	$ 2,817	$ 1,689	$ 1,856	$ 344	$ 3,052	$ 219	$ (698)	$ 34,939	$ 2,917