SEGMENT REPORTING - Reconciliation of Segment Profit to Net Income Attributable to Stockholders (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting [Abstract]
Total Segments' profit	$ 52,337	$ 52,627	$ 159,616	$ 148,385
General and administrative	(5,176)	(4,958)	(16,139)	(15,171)
Depreciation and amortization	(19,886)	(21,192)	(86,033)	(63,360)
Interest expense	12,879	13,873	39,387	39,856
Other (expense) income, net	(125)	(99)	(64)	403
NET INCOME	14,271	12,505	17,993	30,401
Net income attributable to restricted shares	(71)	(60)	(215)	(181)
Net income attributable to unitholders in the Operating Partnership	3,806	3,351	4,765	8,220
NET INCOME ATTRIBUTABLE TO AMERICAN ASSETS TRUST, INC. STOCKHOLDERS	$ 10,394	$ 9,094	$ 13,013	$ 22,000