Consolidated Statement of Equity (Unaudited) - USD ($) $ in Thousands	Total	Interest Expense	Senior Guaranteed Notes, Series A	American Assets Trust, L.P.	American Assets Trust, L.P. Interest Expense	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 realized gains 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 realized gains 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, 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	25,310			25,310
Reclassification of amortization of forward-starting swap realized gains included in interest expense		(665)			(665)
Ending Balance (shares) at Jun. 30, 2020													60,073,918
Ending Balance at Jun. 30, 2020	1,276,488												$ 601		1,454,516	(154,516)	352		(24,465)
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	25,310			25,310
Reclassification of amortization of forward-starting swap realized gains included in interest expense		(665)			(665)
Ending partners' capital account (shares) at Jun. 30, 2020									16,390,548	[1]	60,073,918	[2]
Ending partners' capital account at Jun. 30, 2020				1,276,488			950		$ (25,063)	[1]	$ 1,300,601	[2]
Beginning Balance (shares) at Mar. 31, 2020													60,068,228
Beginning Balance at Mar. 31, 2020	1,281,021												$ 601		1,453,264	(150,226)	603		(23,221)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	9,826			9,826					$ 2,101	[1]	$ 7,725	[2]				7,725			2,101
Issuance of restricted stock (shares)											6,008		6,008
Forfeiture of restricted stock (shares)													(318)
Dividends declared and paid	(15,293)															(12,015)
Dividends declared and paid (noncontrolling interest)																			(3,278)
Stock-based compensation	1,252														1,252
Other comprehensive gain - change in value of interest rate swaps																					14	14	14	10	4
Reclassification of amortization of forward-starting swap realized gains included in interest expense		(332)			(332)		(332)										(261)		(71)
Ending Balance (shares) at Jun. 30, 2020													60,073,918
Ending Balance at Jun. 30, 2020	1,276,488												$ 601		1,454,516	(154,516)	352		(24,465)
Beginning partners' capital account (shares) at Mar. 31, 2020									16,390,548	[1]	60,068,228	[2]
Beginning partners' capital account at Mar. 31, 2020				1,281,021			1,268		$ (23,886)	[1]	$ 1,303,639	[2]
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 9,826			9,826					2,101	[1]	$ 7,725	[2]				7,725			2,101
Issuance of restricted stock (shares)											6,008		6,008
Forfeiture of restricted stock (shares)													(318)
Forfeiture of restricted units											(318)
Distributions				(15,293)					$ (3,278)	[1]	$ (12,015)	[2]
Stock-based compensation				1,252							$ 1,252	[2]
Other comprehensive gain - change in value of interest rate swaps																					14	14	14	10	4
Reclassification of amortization of forward-starting swap realized gains included in interest expense		(332)			(332)		(332)										(261)		(71)
Ending partners' capital account (shares) at Jun. 30, 2020									16,390,548	[1]	60,073,918	[2]
Ending partners' capital account at Jun. 30, 2020				1,276,488			950		$ (25,063)	[1]	$ 1,300,601	[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 realized gains included in interest expense		(275)	$ (193)		(275)	$ (193)	(275)	$ (193)									(216)	$ (152)	(59)	$ (41)
Ending Balance (shares) at Mar. 31, 2021													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 realized gains 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
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	$ 13,220			13,220
Reclassification of amortization of forward-starting swap realized gains included in interest expense		(550)			(550)
Ending Balance (shares) at Jun. 30, 2021	60,474,866												60,474,866
Ending Balance at Jun. 30, 2021	$ 1,227,146												$ 605		1,448,612	(199,955)	2,122		(24,238)
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	13,220			13,220
Reclassification of amortization of forward-starting swap realized gains included in interest expense		(550)			(550)
Ending partners' capital account (shares) at Jun. 30, 2021									16,181,537		60,474,866
Ending partners' capital account at Jun. 30, 2021				1,227,146			3,216		$ (25,332)		$ 1,249,262
Beginning Balance (shares) at Mar. 31, 2021													60,472,286
Beginning Balance at Mar. 31, 2021	1,235,439												$ 605		1,447,128	(192,098)	1,964		(22,160)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	11,487			11,487					$ 2,411		$ 9,076					9,076			2,411
Issuance of restricted stock (shares)											5,184		5,184
Forfeiture of restricted stock (shares)													(2,604)
Dividends declared and paid	(21,464)															(16,933)
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																					475	475	475	374	101
Reclassification of amortization of forward-starting swap realized gains included in interest expense		(275)			(275)		(275)										(216)		(59)
Ending Balance (shares) at Jun. 30, 2021	60,474,866												60,474,866
Ending Balance at Jun. 30, 2021	$ 1,227,146												$ 605		$ 1,448,612	(199,955)	2,122		(24,238)
Beginning partners' capital account (shares) at Mar. 31, 2021									16,181,537		60,472,286
Beginning partners' capital account at Mar. 31, 2021				1,235,439			3,016		$ (23,212)		$ 1,255,635
Increase (Decrease) in Partners' Capital [Roll Forward]
Net income	$ 11,487			11,487					2,411		$ 9,076					$ 9,076			2,411
Issuance of restricted stock (shares)											5,184		5,184
Forfeiture of restricted stock (shares)													(2,604)
Forfeiture of restricted units											(2,604)
Distributions				(21,464)					$ (4,531)		$ (16,933)
Stock-based compensation				1,484							$ 1,484
Other comprehensive gain - change in value of interest rate swaps																					$ 475	$ 475	$ 475	$ 374	$ 101
Reclassification of amortization of forward-starting swap realized gains included in interest expense		$ (275)			$ (275)		(275)										$ (216)		$ (59)
Ending partners' capital account (shares) at Jun. 30, 2021									16,181,537		60,474,866
Ending partners' capital account at Jun. 30, 2021				$ 1,227,146			$ 3,216		$ (25,332)		$ 1,249,262

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

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