INCOME TAXES - Summary of Changes in Deferred Tax Asset Valuation Allowance (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets [Roll Forward]
Balance, January 1,	$ 132,712	$ 164,865	$ 148,310
Increase in deferred tax assets	10,037	27,183	16,555
Remeasurement in deferred tax assets	0	(59,336)	0
Balance, December 31,	$ 142,749	$ 132,712	$ 164,865