SEGMENT REPORTING - Net Real Estate and Secured Note Payable Balances (Details) - USD ($) $ in Thousands		Mar. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net Real Estate		$ 1,823,323	$ 1,831,546
Secured Notes Payable	[1]	316,235	447,028
American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Net Real Estate		1,823,323	1,831,546
Secured notes payable, net | American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Unamortized fair value adjustment and debt issuance costs		500	1,800
Total Retail
Segment Reporting Information [Line Items]
Net Real Estate		625,896	629,261
Secured Notes Payable	[1]	36,249	36,424
Total Office
Segment Reporting Information [Line Items]
Net Real Estate		810,913	813,414
Secured Notes Payable	[1]	206,242	206,550
Total Multifamily
Segment Reporting Information [Line Items]
Net Real Estate		201,955	203,014
Secured Notes Payable	[1]	73,744	73,744
Total Mixed-Use
Segment Reporting Information [Line Items]
Net Real Estate		184,559	185,857
Secured Notes Payable	[1]	$ 0	$ 130,310

[1] Excludes unamortized fair market value adjustments and debt issuance costs of $0.5 million and $1.8 million as of March 31, 2017 and December 31, 2016, respectively.