STOCK-BASED COMPENSATION - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Stock-based compensation expense
Stock-based compensation expense	$ 23,732	$ 18,050	$ 11,520
Cost of sales
Stock-based compensation expense
Stock-based compensation expense	1,064	876	279
Research and development
Stock-based compensation expense
Stock-based compensation expense	4,014	3,744	4,149
General and administrative
Stock-based compensation expense
Stock-based compensation expense	14,597	9,358	5,575
Selling and marketing
Stock-based compensation expense
Stock-based compensation expense	$ 4,057	$ 4,072	$ 1,517