PARTNERS CAPITAL OF AMERICAN ASSETS TRUST, L.P. (Details)	3 Months Ended
	Mar. 31, 2019 shares	Mar. 31, 2018 shares
Operating Partnership Units
Capital Unit [Line Items]
Antidilutive securities excluded from computation of EPS (in shares)	333,275	17,458,586
American Assets Trust, L.P.
Capital Unit [Line Items]
Noncontrolling common units (in shares)	17,177,608
Percentage of ownership interests classified as noncontrolling	26.70%
American Assets Trust, L.P. | Operating Partnership Units
Capital Unit [Line Items]
Antidilutive securities excluded from computation of EPS (in shares)	333,275
Limited Partner | American Assets Trust, L.P.
Capital Unit [Line Items]
Common unit conversion ratio	1
Common Shares | American Assets Trust, L.P.
Capital Unit [Line Items]
Conversion of operating partnership units (in shares)	0