Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018		Dec. 31, 2017
REVENUE:
Rental income	$ 343,865	$ 309,537		$ 298,803
Other property income	22,876	21,330		16,180
Total revenue	366,741	330,867		314,983
EXPENSES:
Rental expenses	91,967	86,482		84,006
Real estate taxes	40,013	34,973		32,671
General and administrative	24,871	22,784		21,382
Depreciation and amortization	96,205	107,093		83,278
Total operating expenses	253,056	251,332		221,337
Operating income (loss)	113,685	79,535		93,646
Interest expense	(54,008)	(52,248)		(53,848)
Gain on sale of real estate	633	0		0
Other income (expense), net	(122)	(85)		334
Net income	60,188	27,202		40,132
Net income attributable to restricted shares	(381)	(311)		(241)
Net income attributable to unitholders in the Operating Partnership	(14,089)	(7,205)		(10,814)
NET INCOME ATTRIBUTABLE TO AMERICAN ASSETS TRUST, INC. STOCKHOLDERS	$ 45,718	$ 19,686		$ 29,077
EARNINGS PER COMMON SHARE, BASIC
Basic net income attributable to common stockholders per share (in dollars per share)	$ 0.84	$ 0.42		$ 0.62
Weighted average shares of common stock outstanding-basic (in shares)	54,110,949	46,950,812		46,715,520
EARNINGS PER COMMON SHARE, DILUTED
Diluted net income attributable to common stockholders per share (in dollars per share)	$ 0.84	$ 0.42		$ 0.62
Weighted average shares of common stock outstanding-diluted (in shares)	70,786,132	64,136,559		64,087,250
COMPREHENSIVE INCOME
Net income	$ 60,188	$ 27,202		$ 40,132
Other comprehensive (loss) gain - unrealized (loss) gain on swap derivative during the period	(5,571)	120		386
Reclassification of amortization of forward starting swap included in interest expense	(1,304)	(1,279)		(1,114)
Comprehensive income	53,313	26,043		39,404
Comprehensive income attributable to noncontrolling interest	(12,301)	(6,877)		(10,433)
Comprehensive income attributable to American Assets Trust, Inc.	41,012	19,166		28,971
American Assets Trust, L.P.
REVENUE:
Rental income	343,865	309,537		298,803
Other property income	22,876	21,330		16,180
Total revenue	366,741	330,867		314,983
EXPENSES:
Rental expenses	91,967	86,482		84,006
Real estate taxes	40,013	34,973		32,671
General and administrative	24,871	22,784		21,382
Depreciation and amortization	96,205	107,093		83,278
Total operating expenses	253,056	251,332		221,337
Operating income (loss)	113,685	79,535		93,646
Interest expense	(54,008)	(52,248)		(53,848)
Gain on sale of real estate	633	0		0
Other income (expense), net	(122)	(85)		334
Net income	60,188	27,202		40,132
Net income attributable to restricted shares	(381)	(311)		(241)
NET INCOME ATTRIBUTABLE TO AMERICAN ASSETS TRUST, INC. STOCKHOLDERS	$ 59,807	$ 26,891		$ 39,891
EARNINGS PER COMMON SHARE, BASIC
Basic net income attributable to common stockholders per share (in dollars per share)	$ 0.84	$ 0.42		$ 0.62
Weighted average shares of common stock outstanding-basic (in shares)	70,786,132	64,136,559		64,087,250
EARNINGS PER COMMON SHARE, DILUTED
Diluted net income attributable to common stockholders per share (in dollars per share)	$ 0.84	$ 0.42		$ 0.62
Weighted average shares of common stock outstanding-diluted (in shares)	70,786,132	64,136,559		64,087,250
DISTRIBUTIONS PER UNIT (in dollars per share)	$ 1.14	$ 1.09		$ 1.05
COMPREHENSIVE INCOME
Net income	$ 60,188	$ 27,202		$ 40,132
Reclassification of amortization of forward starting swap included in interest expense	(1,304)	(1,279)		(1,114)
Comprehensive income	53,313	26,043		39,404
American Assets Trust, L.P. | Limited Partner
EXPENSES:
Net income	14,089	7,205	[1]	10,814	[1]
COMPREHENSIVE INCOME
Net income	14,089	7,205	[1]	10,814	[1]
Comprehensive income attributable to American Assets Trust, Inc.	(12,301)	(6,877)		(10,433)
American Assets Trust, L.P. | General Partner
EXPENSES:
Net income	46,099	19,997	[2]	29,318	[2]
COMPREHENSIVE INCOME
Net income	46,099	19,997	[2]	29,318	[2]
Comprehensive income attributable to American Assets Trust, Inc.	41,012	19,166		28,971
Interest Rate Swap | American Assets Trust, L.P.
COMPREHENSIVE INCOME
Other comprehensive (loss) gain - unrealized (loss) gain on swap derivative during the period	(5,571)	120		386
Swap
COMPREHENSIVE INCOME
Other comprehensive (loss) gain - unrealized (loss) gain on swap derivative during the period	(6,084)	120		(10,281)
Swap | American Assets Trust, L.P.
COMPREHENSIVE INCOME
Other comprehensive (loss) gain - unrealized (loss) gain on swap derivative during the period	(6,084)	$ 120		(10,281)
Forward Contracts
COMPREHENSIVE INCOME
Other comprehensive (loss) gain - unrealized (loss) gain on swap derivative during the period	513			10,667
Forward Contracts | American Assets Trust, L.P.
COMPREHENSIVE INCOME
Other comprehensive (loss) gain - unrealized (loss) gain on swap derivative during the period	$ 513			$ 10,667

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

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