SEGMENT REPORTING - Reconciliation of Segment Profit to Net Income Attributable to Stockholders (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Segment Reporting [Abstract]
Total segments’ profit	$ 63,431			$ 52,337			$ 171,920	$ 159,616
General and administrative	(6,479)			(5,176)			(18,495)	(16,139)
Depreciation and amortization	(26,568)			(19,886)			(69,733)	(86,033)
Interest expense	(13,734)			(12,879)			(40,212)	(39,387)
Gain on sale of real estate	0			0			633	0
Other (expense) income, net	(131)			(125)			(410)	(64)
NET INCOME	16,519	$ 11,941	$ 15,243	14,271	$ 4,413	$ (691)	43,703	17,993
Net income attributable to restricted shares	(92)			(71)			(277)	(215)
Net income attributable to unitholders in the Operating Partnership	3,565			3,806			10,553	4,765
NET INCOME ATTRIBUTABLE TO AMERICAN ASSETS TRUST, INC. STOCKHOLDERS	$ 12,862			$ 10,394			$ 32,873	$ 13,013