PARTNERS' CAPITAL OF AMERICAN ASSETS TRUST, L.P. (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2020 shares	Jun. 30, 2019 shares	Jun. 30, 2020 shares	Jun. 30, 2019 shares
American Assets Trust, L.P.
Capital Unit [Line Items]
Percentage of ownership interests classified as noncontrolling	21.50%		21.50%
Operating Partnership Units
Capital Unit [Line Items]
Antidilutive securities excluded from computation of EPS (in shares)	345,241	330,847	345,199	332,054
American Assets Trust, L.P.
Capital Unit [Line Items]
Noncontrolling common units (in shares)	16,390,548		16,390,548
American Assets Trust, L.P. | Operating Partnership Units
Capital Unit [Line Items]
Weighted average unvested shares outstanding (in shares)	345,241	330,847	345,199	332,054
Antidilutive securities excluded from computation of EPS (in shares)	345,241	330,847	345,199	332,054
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
Common Shares | American Assets Trust, L.P.
Capital Unit [Line Items]
Conversion of operating partnership units (in shares)			0