PARTNERS CAPITAL OF AMERICAN ASSETS TRUST, L.P. (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2019 shares	Jun. 30, 2018 shares	Jun. 30, 2019 shares	Jun. 30, 2018 shares
Operating Partnership Units
Capital Unit [Line Items]
Antidilutive securities excluded from computation of EPS (in shares)	330,847	266,260	332,054	267,367
American Assets Trust, L.P.
Capital Unit [Line Items]
Noncontrolling common units (in shares)	16,390,548		16,390,548
Percentage of ownership interests classified as noncontrolling	21.60%		21.60%
American Assets Trust, L.P. | Operating Partnership Units
Capital Unit [Line Items]
Weighted average unvested shares outstanding (in shares)	330,847	266,260	332,054	267,367
Antidilutive securities excluded from computation of EPS (in shares)	330,847	266,260	332,054	267,367
Limited Partner | American Assets Trust, L.P.
Capital Unit [Line Items]
Common unit conversion ratio			1
Common Shares
Capital Unit [Line Items]
Conversion of operating partnership units (in shares)	787,060	17,372
Common Shares | American Assets Trust, L.P.
Capital Unit [Line Items]
Conversion of operating partnership units (in shares)			787,060