STOCK-BASED COMPENSATION - Allocation of Share-based Compensation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	$ 5,932	$ 6,956	$ 11,188
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	3,109	2,985	5,116
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	1,952	1,052	313
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	570	2,527	5,460
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	301	392	299
Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	133	168	705
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	264	532	844
Selling and Marketing Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	1,197	1,581	4,045
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	$ 4,338	$ 4,675	$ 5,594