EQUITY OF AMERICAN ASSETS TRUST, INC. (Details)			3 Months Ended		9 Months Ended
	Mar. 02, 2018 Agent	May 27, 2015 USD ($) Agent	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($) shares	Sep. 30, 2018 USD ($) shares	Sep. 30, 2017 USD ($) shares
Equity [Line Items]
Noncash compensation expense			$ 700,000	$ 600,000	$ 2,200,000	$ 1,900,000
Unrecognized compensation expense			$ 2,000,000.0		$ 2,000,000.0
Weighted average unvested shares outstanding (in shares) | shares			262,605	231,977	265,762	232,041
At The Market Equity Program
Equity [Line Items]
Number of sales agents | Agent	1	5
Common shares issued (in shares) | shares					0
Aggregate offering price of common share		$ 250,000,000.0
Remaining capacity to issue			$ 176,200,000		$ 176,200,000
Operating Partnership Units
Equity [Line Items]
Antidilutive securities excluded from computation of EPS (in shares) | shares			262,605	231,977	265,762	232,041