DEBT - Summary of Total Secured Notes Payable Outstanding (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt issuance costs, net		$ (1,154)	$ (1,256)
Debt issuance costs, accumulated amortization		916	814
American Assets Trust, L.P. | Secured notes payable, net
Debt Instrument [Line Items]
Long-term Debt, Principal Balance		111,000	162,003
Debt issuance costs, net		(108)	(124)
Total Debt Outstanding		$ 110,892	161,879
Period of amortization schedule (in years)		30 years
Debt issuance costs, accumulated amortization		$ 313	449
American Assets Trust, L.P. | Secured notes payable, net | Torrey Reserve
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[1]	$ 0	6,498
Stated Interest Rate	[1]	6.36%
Stated Maturity Date	[1]	Jun. 01, 2020
American Assets Trust, L.P. | Secured notes payable, net | Solana Beach Corporate Centre One To Two
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[1]	$ 0	10,270
Stated Interest Rate	[1]	5.91%
Stated Maturity Date	[1]	Jun. 01, 2020
American Assets Trust, L.P. | Secured notes payable, net | Solana Beach Towne Centre
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[1]	$ 0	34,235
Stated Interest Rate	[1]	5.91%
Stated Maturity Date	[1]	Jun. 01, 2020
American Assets Trust, L.P. | Secured notes payable, net | City Center Bellevue
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[2]	$ 111,000	$ 111,000
Stated Interest Rate	[2]	3.98%
Stated Maturity Date	[2]	Nov. 01, 2022

[1] Principal payments based on a 30-year amortization schedule.

[2] Interest only.