Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	$ 2,996	$ 939	$ 7,121	$ 7,776
Cost of revenue - product
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	171	138	592	359
Cost of revenue - service
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	412	91	1,055	203
Research and development
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	912	195	1,431	515
Sales and marketing
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	401	158	1,172	440
General and administrative
Stock-based compensation expense
Total stock-based compensation expense (in dollars)	$ 1,100	$ 357	$ 2,871	$ 6,259