STOCK-BASED COMPENSATION - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stock-based compensation expense
Stock-based compensation expense	$ 18,050	$ 11,520	$ 7,744
Cost of sales
Stock-based compensation expense
Stock-based compensation expense	876	279
Research and development
Stock-based compensation expense
Stock-based compensation expense	3,744	4,149	2,817
General and administrative
Stock-based compensation expense
Stock-based compensation expense	9,358	5,575	3,054
Selling and marketing
Stock-based compensation expense
Stock-based compensation expense	$ 4,072	$ 1,517	$ 1,873