Consolidated Statement of Equity (Unaudited) - 6 months ended Jun. 30, 2015 - USD ($) $ in Thousands	Total	Common Shares	Additional Paid-in Capital	Accumulated Dividends in Excess of Net Income	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests - Unitholders in the Operating Partnership	American Assets Trust, L.P.	American Assets Trust, L.P. Common Shares	Limited Partner American Assets Trust, L.P.	General Partner American Assets Trust, L.P.	Accumulated Other Comprehensive Income (Loss) American Assets Trust, L.P.
Beginning Balance (in shares) at Dec. 31, 2014		43,701,669
Beginning Balance at Dec. 31, 2014	$ 766,576	$ 437	$ 795,065	$ (60,291)	$ 92	$ 31,273
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,663			16,818		6,845	$ 23,663		$ 6,845	$ 16,818
Common shares issued (in shares)		1,345,926
Common shares issued	54,007	$ 13	53,994
Issuance of restricted stock (in shares)		5,044
Issuance of restricted stock	0	$ 0	0
Forfeiture of restricted stock (in shares)		(8,405)
Conversion of operating partnership units (in shares)		5,741						5,741
Conversion of operating partnership units	0		67			(67)
Dividends declared and paid	(28,874)			(20,551)		(8,323)
Stock-based compensation	1,724		1,724
Shares withheld for employee taxes (in shares)		(140,045)								(140,045)
Shares withheld for employee taxes	(6,212)	$ (1)	(6,211)				(6,212)			$ (6,212)
Other comprehensive loss - change in value of interest rate swap	(486)				(349)	(137)	(486)				$ (486)
Reclassification of amortization of forward-starting swap included in interest expense	(116)				(82)	(34)	(116)				(116)
Ending Balance (in shares) at Jun. 30, 2015		44,909,930
Ending Balance at Jun. 30, 2015	810,282	$ 449	844,639	(64,024)	(339)	29,557
Beginning Partners' Capital Account, Units at Dec. 31, 2014									17,905,257	43,701,669
Beginning Partners' Capital Account at Dec. 31, 2014							766,576		$ 31,235	$ 735,211	130
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	23,663			$ 16,818		6,845	23,663		$ 6,845	$ 16,818
Contributions from American Assets Trust, Inc. (in shares)										1,345,926
Contributions from American Assets Trust, Inc.							54,007			$ 54,007
Conversion of operating partnership units (in shares)									(5,741)	5,741
Conversion of operating partnership units									$ (67)	$ 67
Issuance of restricted units (in shares)										5,044
Forfeiture of restricted units (in shares)										(8,405)
Distributions							(28,874)		$ (8,323)	$ (20,551)
Stock-based compensation							1,724			$ 1,724
Shares withheld for employee taxes (in shares)		(140,045)								(140,045)
Shares withheld for employee taxes	(6,212)	$ (1)	$ (6,211)				(6,212)			$ (6,212)
Other comprehensive income (loss) - unrealized gain (loss) on swap derivative during the period	(486)				(349)	(137)	(486)				(486)
Reclassification of amortization of forward-starting swap included in interest expense	$ (116)				$ (82)	$ (34)	(116)				(116)
Ending Partners' Capital Account, Units at Jun. 30, 2015									17,899,516	44,909,930
Ending Partners' Capital Account at Jun. 30, 2015							$ 810,282		$ 29,690	$ 781,064	$ (472)