INCOME TAXES - SCHEDULE OF EFFECTIVE INCOME TAX RATE RECONCILIATION (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income tax (benefit) provision at the federal statutory rate of 35%	$ (53,771)	$ 7,862	$ (783)
Change in tax reserves, net	235	(72)	1,895
State income taxes, net of effect of federal tax benefit	(3,678)	1,063	(39)
Unbenefited losses	5,915	2,592	1,133
Research credit	(784)	(930)	(645)
Federal tax rate change to 21%	33,002	0	0
Stock-based compensation	(32,702)	0	0
Other, net	2,677	1,319	197
Income tax (benefit) provision	$ (49,106)	$ 11,834	$ 1,758