Consolidated Statement of Equity (Unaudited) - 6 months ended Jun. 30, 2018 - 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	Swap	Swap American Assets Trust, L.P.	Swap American Assets Trust, L.P. Accumulated Other Comprehensive Income (Loss)	Swap Accumulated Other Comprehensive Income (Loss)	Swap Noncontrolling Interests - Unitholders in the Operating Partnership
Beginning Balance (in shares) at Dec. 31, 2017									47,204,588
Beginning Balance at Dec. 31, 2017		$ 844,144							$ 473		$ 919,066	$ (97,280)	$ 11,451	$ 10,434
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		3,722	$ 3,722		$ 959		$ 2,763	[2]				2,763		959
Issuance of restricted stock (in shares)									5,320
Issuance of restricted shares									$ 0		0
Forfeiture of restricted stock (in shares)									(3,312)
Forfeiture of restricted stock		0							$ 0		0
Conversion of operating partnership units (in shares)									17,372	17,372
Conversion of operating partnership units									$ 0		(916)			916
Dividends declared and paid		(34,776)										(25,491)
Dividends declared and paid (noncontrolling interest)														(9,285)
Stock-based compensation		1,454									1,454
Shares withheld for employee taxes (in shares)							(159)	[2]	(159)
Shares withheld for employee taxes		(6)	(6)				$ (6)	[2]	$ 0		(6)
Other comprehensive income - change in value of interest rate swaps		3,736	3,736												$ 3,736	$ 3,736	$ 3,736	$ 2,750	$ 986
Reclassification of amortization of forward-starting swap included in interest expense		(639)	(639)	$ (639)									(467)	(172)
Ending Balance (in shares) at Jun. 30, 2018									47,223,809
Ending Balance at Jun. 30, 2018		817,635							$ 473		919,598	(120,008)	13,734	3,838
Beginning partners' capital account (in shares) at Dec. 31, 2017					17,194,980		47,204,588	[2]
Beginning partners' capital account at Dec. 31, 2017			844,144	15,750	$ 6,135		$ 822,259	[2]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		3,722	3,722		$ 959		$ 2,763	[2]				$ 2,763		959
Conversion of operating partnership units (in shares)					17,372		17,372	[2]
Conversion of operating partnership units					$ 916		$ (916)	[2]
Issuance of restricted units (in shares)	[2]						5,320
Forfeiture of restricted units (in shares)	[2]						(3,312)
Distributions			(34,776)		$ (9,285)		$ (25,491)	[2]
Stock-based compensation			1,454				$ 1,454	[2]
Shares withheld for employee taxes (in shares)							(159)	[2]	(159)
Shares withheld for employee taxes		(6)	(6)				$ (6)	[2]	$ 0		$ (6)
Other comprehensive income (loss) - unrealized income (loss) on swap derivative during the period		3,736	3,736												$ 3,736	$ 3,736	$ 3,736	$ 2,750	$ 986
Reclassification of amortization of forward-starting swap included in interest expense		$ (639)	(639)	(639)									$ (467)	$ (172)
Ending partners' capital account (in shares) at Jun. 30, 2018					17,177,608		47,223,809	[2]
Ending partners' capital account at Jun. 30, 2018			$ 817,635	$ 18,847	$ (1,275)		$ 800,063	[2]

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

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