Debt Summary of Total Secured Notes Payable Outstanding (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Debt issuance costs, net	$ (1,256)	$ 0
Notes payable, total	1,362,003
Debt issuance costs, accumulated amortization	814	0
Secured notes payable \| American Assets Trust, L.P.
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	162,003	182,765
Debt issuance costs, net	(124)	(193)
Notes payable, total	$ 161,879	182,572
Number of year amortization schedule	30 years
Debt issuance costs, accumulated amortization	$ 449	671
Secured notes payable \| American Assets Trust, L.P. \| Torrey Reserve - North Court
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	$ 0	19,620
Stated Interest Rate	7.22%
Stated Maturity Date	Jun. 01, 2019
Secured notes payable \| American Assets Trust, L.P. \| Torrey Reserve-VCI, VCII, VCIII
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	$ 6,498	6,635
Stated Interest Rate	6.36%
Stated Maturity Date	Jun. 01, 2020
Secured notes payable \| American Assets Trust, L.P. \| Solana Beach Corporate Centre I-II
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	$ 10,270	10,502
Stated Interest Rate	5.91%
Stated Maturity Date	Jun. 01, 2020
Secured notes payable \| American Assets Trust, L.P. \| Solana Beach Towne Centre
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	$ 34,235	35,008
Stated Interest Rate	5.91%
Stated Maturity Date	Jun. 01, 2020
Secured notes payable \| American Assets Trust, L.P. \| City Center Bellevue
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	$ 111,000	$ 111,000
Stated Interest Rate	3.98%
Stated Maturity Date	Nov. 01, 2022

Amount of accumulated amortization of debt issuance costs.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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