Consolidated Statement of Equity (Unaudited) - USD ($) $ in Thousands	Total	Senior Guaranteed Notes, Series A	American Assets Trust, L.P.	American Assets Trust, L.P. Senior Guaranteed Notes, Series A	American Assets Trust, L.P. Accumulated Other Comprehensive Income (Loss)	American Assets Trust, L.P. Accumulated Other Comprehensive Income (Loss) Senior Guaranteed Notes, Series A	American Assets Trust, L.P. Limited Partner		American Assets Trust, L.P. General Partner		Common Shares	Common Shares American Assets Trust, L.P. General Partner	Additional Paid-in Capital	Accumulated Dividends in Excess of Net Income	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Senior Guaranteed Notes, Series A	Noncontrolling Interests - Unitholders in the Operating Partnership	Noncontrolling Interests - Unitholders in the Operating Partnership Senior Guaranteed Notes, Series A	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, 2019											60,068,228
Beginning Balance at Dec. 31, 2019	$ 1,293,672										$ 601		$ 1,452,014	$ (144,378)	$ 5,680		$ (20,245)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,484		$ 15,484				$ 3,312	[1]	$ 12,172	[2]				12,172			3,312
Dividends declared and paid	(22,937)													(18,020)
Dividends declared and paid (noncontrolling interest)																	(4,917)
Stock-based compensation	1,250												1,250
Other comprehensive gain - change in value of interest rate swaps																			$ (6,115)	$ (6,115)	$ (6,115)	$ (4,816)	$ (1,299)
Reclassification of amortization of forward-starting swap included in interest expense	(333)		(333)		$ (333)										(261)		(72)
Ending Balance (shares) at Mar. 31, 2020											60,068,228
Ending Balance at Mar. 31, 2020	1,281,021										$ 601		1,453,264	(150,226)	603		(23,221)
Beginning partners' capital account (shares) at Dec. 31, 2019							16,390,548	[1]	60,068,228	[2]
Beginning partners' capital account at Dec. 31, 2019			1,293,672		7,716		$ (22,281)	[1]	$ 1,308,237	[2]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	15,484		15,484				3,312	[1]	12,172	[2]				12,172			3,312
Distributions			(22,937)				$ (4,917)	[1]	(18,020)	[2]
Stock-based compensation			1,250						$ 1,250	[2]
Other comprehensive gain - change in value of interest rate swaps																			(6,115)	(6,115)	(6,115)	(4,816)	(1,299)
Reclassification of amortization of forward-starting swap included in interest expense	$ (333)		(333)		(333)										(261)		(72)
Ending partners' capital account (shares) at Mar. 31, 2020							16,390,548	[1]	60,068,228	[2]
Ending partners' capital account at Mar. 31, 2020			1,281,021		1,268		$ (23,886)	[1]	$ 1,303,639	[2]
Beginning Balance (shares) at Dec. 31, 2020	60,476,292										60,476,292
Beginning Balance at Dec. 31, 2020	$ 1,253,406										$ 605		1,445,644	(176,560)	1,753		(18,036)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,733		1,733				$ 339	[1]	$ 1,394	[2]				1,394			339
Forfeiture of restricted stock (shares)											(4,006)	(4,006)
Dividends declared and paid	(21,463)													(16,932)
Dividends declared and paid (noncontrolling interest)																	(4,531)
Stock-based compensation	1,484												1,484
Other comprehensive gain - change in value of interest rate swaps																			747	747	747	579	168
Reclassification of amortization of forward-starting swap included in interest expense	$ (275)	$ (193)	(275)	$ (193)	(275)	$ (193)									(216)	$ (152)	(59)	$ (41)
Ending Balance (shares) at Mar. 31, 2021	60,472,286										60,472,286
Ending Balance at Mar. 31, 2021	$ 1,235,439										$ 605		$ 1,447,128	(192,098)	1,964		(22,160)
Beginning partners' capital account (shares) at Dec. 31, 2020							16,181,537		60,476,292
Beginning partners' capital account at Dec. 31, 2020			1,253,406		2,737		$ (19,020)		$ 1,269,689
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	1,733		1,733				339	[1]	1,394	[2]				$ 1,394			339
Forfeiture of restricted stock (shares)											(4,006)	(4,006)
Distributions			(21,463)				$ (4,531)	[1]	(16,932)	[2]
Stock-based compensation			1,484						$ 1,484	[2]
Other comprehensive gain - change in value of interest rate swaps																			$ 747	$ 747	$ 747	$ 579	$ 168
Reclassification of amortization of forward-starting swap included in interest expense	$ (275)	$ (193)	(275)	$ (193)	(275)	$ (193)									$ (216)	$ (152)	$ (59)	$ (41)
Ending partners' capital account (shares) at Mar. 31, 2021							16,181,537		60,472,286
Ending partners' capital account at Mar. 31, 2021			$ 1,235,439		$ 3,016		$ (23,212)		$ 1,255,635

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

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