REAL ESTATE (Details) $ in Thousands			1 Months Ended	3 Months Ended							9 Months Ended
	Sep. 10, 2021 USD ($) ft²	Jul. 07, 2021 USD ($) ft²	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Real Estate [Line Items]
Acquired in-place leases, net			$ 31,504	$ 31,504	$ 31,504						$ 31,504		$ 26,207
Prepaid expenses and other			8,795	8,795	8,795						8,795		8,702
Assets			3,051,070	3,051,070	3,051,070						3,051,070		2,817,309
Accounts payable and accrued expenses			(88,851)	(88,851)	(88,851)						(88,851)		(59,262)
Security deposits payable			(7,996)	(7,996)	(7,996)						(7,996)		(6,590)
Other liabilities and deferred credits, net			(86,805)	(86,805)	(86,805)						(86,805)		(91,300)
Liabilities			(1,832,379)	(1,832,379)	(1,832,379)						(1,832,379)		(1,563,903)
Revenues				98,286				$ 84,374			274,081	$ 263,226
Operating Income (Loss)				27,669				20,323			74,154	72,166
Net income				12,895		$ 11,487	$ 1,733	6,490	$ 9,826	$ 15,484	26,115	31,800
American Assets Trust, L.P.
Real Estate [Line Items]
Assets			3,051,070	3,051,070	3,051,070						3,051,070		2,817,309
Accounts payable and accrued expenses			(88,851)	(88,851)	(88,851)						(88,851)		(59,262)
Security deposits payable			(7,996)	(7,996)	(7,996)						(7,996)		(6,590)
Other liabilities and deferred credits, net			(86,805)	(86,805)	(86,805)						(86,805)		(91,300)
Liabilities			(1,832,379)	(1,832,379)	(1,832,379)						(1,832,379)		$ (1,563,903)
Revenues				98,286				84,374			274,081	263,226
Operating Income (Loss)				27,669				20,323			74,154	72,166
Net income				12,895		$ 11,487	$ 1,733	$ 6,490	$ 9,826	$ 15,484	26,115	$ 31,800
Office Building
Real Estate [Line Items]
Revenues					2,796
Operating Expenses					(3,055)
Operating Income (Loss)					(259)
Net income					(258)
Office Building | Eastgate Office Park
Real Estate [Line Items]
Area of Real Estate Property | ft²		280,000
Payments to Acquire Productive Assets		$ 125,000
Acquisition Cost Capitalized		$ 200
Land			35,822	35,822	35,822						35,822
Buildings and Improvements, Gross			76,692	76,692	76,692						76,692
Land Improvements			1,740	1,740	1,740						1,740
Furniture and Fixtures, Gross			4,305	4,305	4,305						4,305
Property, Plant and Equipment, Gross			118,559	118,559	118,559						118,559
Acquired in-place leases, net			7,023	7,023	7,023						7,023
Prepaid expenses and other			8	8	8						8
Assets			125,590	125,590	125,590						125,590
Accounts payable and accrued expenses			(31)	(31)	(31)						(31)
Security deposits payable			(513)	(513)	(513)						(513)
Other liabilities and deferred credits, net			(535)	(535)	(535)						(535)
Liabilities			(1,079)	(1,079)	(1,079)						$ (1,079)
Revenues					2,432
Operating Expenses					(2,572)
Operating Income (Loss)					(140)
Net income					(139)
Office Building | Eastgate Office Park | Leases
Real Estate [Line Items]
Weighted average useful life (in years)											3 years 6 months
Office Building | Corporate Campus East III
Real Estate [Line Items]
Area of Real Estate Property | ft²	161,000
Payments to Acquire Productive Assets	$ 84,000
Purchase price seller credits, future rent abatement	1,100
Purchase price seller credits, contractual tenant improvements	2,100
Acquisition Cost Capitalized	$ 100
Land			23,203	23,203	23,203						$ 23,203
Buildings and Improvements, Gross			52,234	52,234	52,234						52,234
Land Improvements			667	667	667						667
Furniture and Fixtures, Gross			3,091	3,091	3,091						3,091
Property, Plant and Equipment, Gross			79,195	79,195	79,195						79,195
Acquired in-place leases, net			5,341	5,341	5,341						5,341
Prepaid expenses and other			13	13	13						13
Assets			84,549	84,549	84,549						84,549
Accounts payable and accrued expenses			(9)	(9)	(9)						(9)
Security deposits payable			(310)	(310)	(310)						(310)
Other liabilities and deferred credits, net			(3,844)	(3,844)	(3,844)						(3,844)
Liabilities			(4,163)	$ (4,163)	$ (4,163)						$ (4,163)
Revenues			364
Operating Expenses			(483)
Operating Income (Loss)			(119)
Net income			$ (119)
Office Building | Corporate Campus East III | Leases
Real Estate [Line Items]
Weighted average useful life (in years)											5 years 6 months