Consolidated Statement of Equity (Unaudited) - USD ($)		Total	American Assets Trust, L.P.	American Assets Trust, L.P. Accumulated Other Comprehensive Income (Loss)	American Assets Trust, L.P. Limited Partner		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 (shares) at Dec. 31, 2018									47,335,409
Beginning Balance at Dec. 31, 2018		$ 802,471,000							$ 474,000		$ 920,661,000	$ (128,778,000)	$ 10,620,000	$ (506,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		15,243,000	$ 15,243,000		$ 4,055,000	[1]	$ 11,188,000	[2]				11,188,000		4,055,000
Common shares issued (shares)									162,531
Common shares issued		7,034,000	7,034,000						$ 1,000		7,033,000
Forfeiture of restricted stock (shares)									(11,046)
Dividends declared and paid		(18,061,000)										(13,251,000)
Dividends declared and paid (noncontrolling interest)														(4,810,000)
Stock-based compensation		1,098,000									1,098,000
Other comprehensive loss - change in value of interest rate swaps															$ (2,132,000)	$ (2,132,000)	$ (2,132,000)	$ (1,561,000)	$ (571,000)
Reclassification of amortization of forward-starting swap included in interest expense		320,000	320,000	$ 320,000									234,000	86,000
Ending Balance (shares) at Mar. 31, 2019									47,486,894
Ending Balance at Mar. 31, 2019		805,333,000							$ 475,000		928,792,000	(130,841,000)	8,825,000	(1,918,000)
Beginning partners' capital account (shares) at Dec. 31, 2018					17,177,608	[1]	47,335,409	[2]
Beginning partners' capital account at Dec. 31, 2018			802,471,000	14,591,000	$ (4,477,000)	[1]	$ 792,357,000	[2]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		15,243,000	15,243,000		4,055,000	[1]	$ 11,188,000	[2]				11,188,000		4,055,000
Contributions from American Assets Trust, Inc. (in shares)							162,531
Partners' Capital Account, Contributions							$ 7,034,000
Partners' Capital Account, Restricted Units Forfeiture	[2]						(11,046)
Distributions			(18,061,000)		$ (4,810,000)	[1]	$ (13,251,000)	[2]
Partners' Capital Account, Unit-based Payment Arrangement, Amount			1,098,000				$ 1,098,000	[2]
Other comprehensive loss - change in value of interest rate swaps															(2,132,000)	(2,132,000)	(2,132,000)	(1,561,000)	(571,000)
Reclassification of amortization of forward-starting swap included in interest expense		320,000	320,000	320,000									234,000	86,000
Ending partners' capital account (shares) at Mar. 31, 2019					17,177,608	[1]	47,486,894	[2]
Ending partners' capital account at Mar. 31, 2019			805,333,000	12,139,000	$ (5,232,000)	[1]	$ 798,426,000	[2]
Beginning Balance (shares) at Dec. 31, 2019									60,068,228
Beginning Balance at Dec. 31, 2019		1,293,672,000							$ 601,000		1,452,014,000	(144,378,000)	5,680,000	(20,245,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income		15,484,000	15,484,000		$ 3,312,000	[1]	$ 12,172,000	[2]				12,172,000		3,312,000
Conversion of operating partnership units (in shares)										0
Dividends declared and paid		(22,937,000)										(18,020,000)
Dividends declared and paid (noncontrolling interest)														(4,917,000)
Stock-based compensation		1,250,000									1,250,000
Other comprehensive loss - change in value of interest rate swaps															(6,115,000)	(6,115,000)	(6,115,000)	(4,816,000)	(1,299,000)
Reclassification of amortization of forward-starting swap included in interest expense		333,000	333,000	333,000									261,000	72,000
Ending Balance (shares) at Mar. 31, 2020									60,068,228
Ending Balance at Mar. 31, 2020		1,281,021,000							$ 601,000		$ 1,453,264,000	(150,226,000)	603,000	(23,221,000)
Beginning partners' capital account (shares) at Dec. 31, 2019					16,390,548		60,068,228
Beginning partners' capital account at Dec. 31, 2019			1,293,672,000	7,716,000	$ (22,281,000)		$ 1,308,237,000
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income		15,484,000	15,484,000		3,312,000	[1]	12,172,000	[2]				$ 12,172,000		3,312,000
Distributions			(22,937,000)		$ (4,917,000)	[1]	(18,020,000)	[2]
Partners' Capital Account, Unit-based Payment Arrangement, Amount			1,250,000				$ 1,250,000	[2]
Other comprehensive loss - change in value of interest rate swaps															$ (6,115,000)	$ (6,115,000)	$ (6,115,000)	$ (4,816,000)	$ (1,299,000)
Reclassification of amortization of forward-starting swap included in interest expense		$ 333,000	333,000	333,000									$ 261,000	$ 72,000
Ending partners' capital account (shares) at Mar. 31, 2020					16,390,548		60,068,228
Ending partners' capital account at Mar. 31, 2020			$ 1,281,021,000	$ 1,268,000	$ (23,886,000)		$ 1,303,639,000

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

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