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
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	$ 7,225	$ 2,996	$ 20,983	$ 7,121
Cost of revenue - product
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	290	171	912	592
Cost of revenue - service
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	928	412	2,906	1,055
Research and development
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	2,053	912	6,141	1,431
Sales and marketing
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	1,132	401	3,224	1,172
General and administrative
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	$ 2,822	$ 1,100	$ 7,800	$ 2,871