Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	490,000,000	490,000,000
Common stock, shares issued	60,476,292	60,068,228
Common stock, shares outstanding	60,476,292	60,068,228
American Assets Trust, L.P.
Limited Partners' Capital Account, Units Issued	16,181,537	16,390,548
Limited Partners' Capital Account, Units Outstanding	16,181,537	16,390,548
General Partners' Capital Account, Units Issued	60,476,292	60,068,228
General Partners' Capital Account, Units Outstanding	60,476,292	60,068,228