SEGMENT REPORTING - Reconciliation of Segment Profit to Net Income Attributable to Stockholders (Details) - USD ($) $ in Thousands	3 Months Ended		5 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting [Abstract]
Total Segments' profit	$ 52,627	$ 47,989		$ 148,385	$ 139,446
General and administrative	(4,958)	(4,513)		(15,171)	(13,456)
Depreciation and amortization	(21,192)	(17,992)		(63,360)	(53,159)
Interest expense	13,873	13,049		39,856	39,148
Other (expense) income, net	(99)	(577)		403	(454)
NET INCOME	12,505	11,858	$ (4,622)	30,401	33,229
Net income attributable to restricted shares	(60)	(42)		(181)	(128)
Net income attributable to unitholders in the Operating Partnership	3,351	3,342		8,220	9,377
NET INCOME ATTRIBUTABLE TO AMERICAN ASSETS TRUST, INC. STOCKHOLDERS	$ 9,094	$ 8,474		$ 22,000	$ 23,724