Stockholders' Equity - Non-cash Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 11,022	$ 8,399	$ 34,779	$ 24,174
Cost of revenues
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	637	470	1,967	1,300
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	3,476	2,097	9,674	7,180
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	3,932	3,600	11,015	10,349
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation	$ 2,977	$ 2,232	$ 12,123	$ 5,345