DEBT - Summary of Total Secured Notes Payable Outstanding (Details) - American Assets Trust, L.P. - Secured notes payable, net - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Long-term Debt, Principal Balance		$ 162,856	$ 182,765
Debt issuance costs, net		(168)	(193)
Total Debt Outstanding		$ 162,688	182,572
Period of amortization schedule (in years)		30 years
Debt issuance costs, accumulated amortization		$ 406	671
Torrey Reserve North Court
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[1],[2]	$ 0	19,620
Stated Interest Rate	[1],[2]	7.22%
Stated Maturity Date	[1],[2]	Jun. 01, 2019
Torrey Reserve
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[2]	$ 6,600	6,635
Stated Interest Rate	[2]	6.36%
Stated Maturity Date	[2]	Jun. 01, 2020
Solana Beach Corporate Centre One To Two
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[2]	$ 10,444	10,502
Stated Interest Rate	[2]	5.91%
Stated Maturity Date	[2]	Jun. 01, 2020
Solana Beach Towne Centre
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[2]	$ 34,812	35,008
Stated Interest Rate	[2]	5.91%
Stated Maturity Date	[2]	Jun. 01, 2020
City Center Bellevue
Debt Instrument [Line Items]
Long-term Debt, Principal Balance	[3]	$ 111,000	$ 111,000
Stated Interest Rate	[3]	3.98%
Stated Maturity Date	[3]	Nov. 01, 2022

[1] Loan repaid in full, without premium or penalty, on March 1, 2019.

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

[3] Interest only.