STOCK-BASED COMPENSATION Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	$ 4,969	$ 4,416
Stock Options
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense		100
Performance Based Awards and Long Term Performance based Units
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	1,200	700
Restricted Stock Units (RSUs)
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	3,500	3,300
Employee Stock Purchase Plan
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	300	300
Cost of revenues
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	143	90
Research and development
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	1,634	1,469
Sales and marketing
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	1,097	1,027
General and administrative
Stock-based compensation expense for stock options, stock awards and employee stock purchases included in operations:
Stock-Based Compensation Expense	$ 2,095	$ 1,830