Stock-based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	$ 7,743	$ 5,103	$ 18,522	$ 15,122
Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized employee compensation cost	18,200		$ 18,200
Unrecognized employee compensation cost, period for recognition			2 years 6 months
Restricted Stock Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Unrecognized employee compensation cost	31,900		$ 31,900
Unrecognized employee compensation cost, period for recognition			2 years 9 months 18 days
Cost of revenues
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	532	516	$ 1,569	1,318
Research and development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	1,503	1,585	4,229	4,373
Sales and marketing
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	1,231	821	3,444	3,459
General and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total employee stock-based compensation	$ 4,477	$ 2,181	$ 9,280	$ 5,972