Consolidated Statement of Equity (Unaudited) - 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	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 (loss)		(691)	$ (691)		$ (166)		$ (525)	[2]			(525)		(166)
Forfeiture of restricted stock (in shares)									(1,104)
Dividends declared and paid		(17,388)									(12,745)
Dividends declared and paid (noncontrolling interest)													(4,643)
Stock-based compensation		727								727
Other comprehensive income - change in value of interest rate swaps		2,861	2,861											$ 2,861	$ 2,861	$ 2,861	$ 2,107	$ 754
Reclassification of amortization of forward-starting swap included in interest expense		(320)	(320)	$ (320)								(234)	(86)
Ending Balance (in shares) at Mar. 31, 2018									47,203,484
Ending Balance at Mar. 31, 2018		829,333							$ 473	919,793	(110,550)	13,324	6,293
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		(691)	(691)		(166)		$ (525)	[2]			(525)		(166)
Forfeiture of restricted units (in shares)	[2]						(1,104)
Distributions			(17,388)		$ (4,643)		$ (12,745)	[2]
Stock-based compensation			727				$ 727	[2]
Other comprehensive (loss) income - unrealized (loss) income on swap derivative during the period		2,861	2,861											2,861	2,861	2,861	2,107	754
Reclassification of amortization of forward-starting swap included in interest expense		(320)	(320)	(320)								(234)	(86)
Ending partners' capital account (in shares) at Mar. 31, 2018					17,194,980		47,203,484	[2]
Ending partners' capital account at Mar. 31, 2018			829,333	18,291	$ 1,326		$ 809,716	[2]
Beginning Balance (in shares) at Dec. 31, 2018									47,335,409
Beginning Balance at Dec. 31, 2018		802,471							$ 474	920,661	(128,778)	10,620	(506)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)		15,243	15,243		$ 4,055		$ 11,188	[2]			11,188		4,055
Common shares issued (in shares)									162,531
Common shares issued		7,034							$ 1	7,033
Forfeiture of restricted stock (in shares)									(11,046)
Forfeiture of restricted stock									$ 0	0
Dividends declared and paid		(18,061)									(13,251)
Dividends declared and paid (noncontrolling interest)													(4,810)
Stock-based compensation		1,098								1,098
Other comprehensive income - change in value of interest rate swaps		(2,132)	(2,132)											(2,132)	(2,132)	(2,132)	(1,561)	(571)
Reclassification of amortization of forward-starting swap included in interest expense		(320)	(320)	(320)								(234)	(86)
Ending Balance (in shares) at Mar. 31, 2019									47,486,894
Ending Balance at Mar. 31, 2019		805,333							$ 475	$ 928,792	(130,841)	8,825	(1,918)
Beginning partners' capital account (in shares) at Dec. 31, 2018					17,177,608		47,335,409	[2]
Beginning partners' capital account at Dec. 31, 2018			802,471	14,591	$ (4,477)		$ 792,357	[2]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		15,243	15,243		4,055		$ 11,188	[2]			$ 11,188		4,055
Contributions from American Assets Trust, Inc. (in shares)	[2]						162,531
Contributions from American Assets Trust, Inc.			7,034				$ 7,034	[2]
Forfeiture of restricted units (in shares)	[2]						(11,046)
Distributions			(18,061)		$ (4,810)		$ (13,251)	[2]
Stock-based compensation			1,098				$ 1,098	[2]
Other comprehensive (loss) income - unrealized (loss) income on swap derivative during the period		(2,132)	(2,132)											$ (2,132)	$ (2,132)	$ (2,132)	$ (1,561)	$ (571)
Reclassification of amortization of forward-starting swap included in interest expense		$ (320)	(320)	(320)								$ (234)	$ (86)
Ending partners' capital account (in shares) at Mar. 31, 2019					17,177,608		47,486,894	[2]
Ending partners' capital account at Mar. 31, 2019			$ 805,333	$ 12,139	$ (5,232)		$ 798,426	[2]

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

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