INCOME TAXES - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefits, beginning of period	$ 17,144	$ 14,687	$ 5,686
Gross increases—current year tax positions	262	3,423	240
Gross increases—prior year tax positions			8,761
Gross decreases - prior year tax positions	(1,342)	(966)
Unrecognized tax benefits, end of period	$ 16,064	$ 17,144	$ 14,687