Consolidated Statement of Equity (Unaudited) - 9 months ended Sep. 30, 2016 - USD ($) $ in Thousands		Total	American Assets Trust, L.P.	American Assets Trust, L.P. Accumulated Other Comprehensive Income (Loss)	American Assets Trust, L.P. Limited Partner	[1]	American Assets Trust, L.P. General Partner		Common Shares	Common Shares American Assets Trust, L.P.	Additional Paid-in Capital	Accumulated Dividends in Excess of Net Income	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests - Unitholders in the Operating Partnership
Beginning Balance (in shares) at Dec. 31, 2015									45,407,719
Beginning Balance at Dec. 31, 2015		$ 828,927							$ 454		$ 863,432	$ (64,066)	$ (258)	$ 29,365
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		33,229	$ 33,229		$ 9,377		$ 23,852	[2]				23,852		9,377
Common shares issued (in shares)									219,480
Common shares issued		9,665							$ 2		9,663
Issuance of restricted stock (in shares)									4,900
Issuance of restricted stock		0							$ 0		0
Forfeiture of restricted stock (in shares)									(1,496)
Forfeiture of restricted stock		0							$ 0		0
Conversion of operating partnership units (in shares)									10,694	10,694
Conversion of operating partnership units		0									(79)			79
Dividends declared and paid		(47,536)										(34,114)		(13,422)
Stock-based compensation		1,855									1,855
Shares withheld for employee taxes (in shares)							(317)	[2]	(317)
Shares withheld for employee taxes		(12)	(12)				$ (12)	[2]	$ 0		(12)
Other comprehensive loss - change in value of interest rate swaps		(11,443)	(11,443)	$ (11,443)									(8,201)	(3,242)
Reclassification of amortization of forward-starting swap included in interest expense		(173)	(173)	(173)									(124)	(49)
Ending Balance (in shares) at Sep. 30, 2016									45,640,980
Ending Balance at Sep. 30, 2016		814,512							$ 456		874,859	(74,328)	(8,583)	22,108
Beginning partners' capital account (in shares) at Dec. 31, 2015					17,899,516		45,407,719	[2]
Beginning partners' capital account at Dec. 31, 2015			828,927	(339)	$ 29,446		$ 799,820	[2]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		33,229	33,229		$ 9,377		$ 23,852	[2]				$ 23,852		9,377
Contributions from American Assets Trust, Inc. (in shares)	[2]						219,480
Contributions from American Assets Trust, Inc.			9,665				$ 9,665	[2]
Conversion of operating partnership units (in shares)					(10,694)		10,694	[2]
Conversion of operating partnership units					$ 79		$ (79)	[2]
Issuance of restricted units (in shares)	[2]						4,900
Forfeiture of restricted units (in shares)	[2]						1,496
Distributions			(47,536)		$ (13,422)		$ (34,114)	[2]
Stock-based compensation			1,855				$ 1,855	[2]
Shares withheld for employee taxes (in shares)							(317)	[2]	(317)
Shares withheld for employee taxes		(12)	(12)				$ (12)	[2]	$ 0		$ (12)
Other comprehensive income (loss) - unrealized gain (loss) on swap derivative during the period		(11,443)	(11,443)	(11,443)									(8,201)	(3,242)
Reclassification of amortization of forward-starting swap included in interest expense		$ (173)	(173)	(173)									$ (124)	$ (49)
Ending partners' capital account (in shares) at Sep. 30, 2016					17,888,822		45,640,980	[2]
Ending partners' capital account at Sep. 30, 2016			$ 814,512	$ (11,955)	$ 25,480		$ 800,987	[2]

[1] Consists of limited partnership interests held by third parties.

[2] Consists of general partnership interests held by American Assets Trust, Inc.