STOCK-BASED COMPENSATION - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock-based compensation
Total	$ 12,585	$ 13,016	$ 17,172
Cost of sales
Stock-based compensation
Total	30	98	43
Research and development expense
Stock-based compensation
Total	446	710	496
Selling, general and administrative expense
Stock-based compensation
Total	9,963	12,157	16,633
Restructuring charges
Stock-based compensation
Total	$ 2,146	$ 51	$ 0