Subsequent Events (Details) - Subsequent Event $ in Millions	Jan. 23, 2019 USD ($)	Jan. 09, 2019 Extension_Option
Subsequent Event [Line Items]
Lease termination fee | $	$ 4.4
Unsecured debt | American Assets Trust, L.P. | Term Loan A
Subsequent Event [Line Items]
Number of extensions available | Extension_Option		3
Extension term (in months)		1 year
LIBOR | Unsecured debt | American Assets Trust, L.P. | Term Loan A
Subsequent Event [Line Items]
Variable rate basis		LIBOR
Base Rate | Unsecured debt | American Assets Trust, L.P. | Term Loan A
Subsequent Event [Line Items]
Prime rate		prime rate
Federal funds rate		federal funds rate
Eurodollar		Eurodollar
Federal Funds Rate | Unsecured debt | Term Loan A
Subsequent Event [Line Items]
Basis spread on federal funds rate		0.50%
Eurodollar | Unsecured debt | Term Loan A
Subsequent Event [Line Items]
Basis spread on Eurodollar rate		1.00%
Minimum | LIBOR | Unsecured debt | American Assets Trust, L.P. | Term Loan A
Subsequent Event [Line Items]
Basis spread on variable rate (in percents)		1.20%
Minimum | Base Rate | American Assets Trust, L.P. | Term Loan A
Subsequent Event [Line Items]
Basis spread on variable rate (in percents)		0.20%
Maximum | LIBOR | Unsecured debt | American Assets Trust, L.P. | Term Loan A
Subsequent Event [Line Items]
Basis spread on variable rate (in percents)		1.70%
Maximum | Base Rate | American Assets Trust, L.P. | Term Loan A
Subsequent Event [Line Items]
Basis spread on variable rate (in percents)		0.70%