Stock-Based Compensation - Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Stock-based compensation expense
Total Stock-based compensation expense (in dollars)	$ 1,945	$ 3,821
Cost of revenue - product
Stock-based compensation expense
Total Stock-based compensation expense (in dollars)	250	95
Cost of revenue - service
Stock-based compensation expense
Total Stock-based compensation expense (in dollars)	270	43
Research and development
Stock-based compensation expense
Total Stock-based compensation expense (in dollars)	196	104
Sales and marketing
Stock-based compensation expense
Total Stock-based compensation expense (in dollars)	379	117
General and administrative
Stock-based compensation expense
Total Stock-based compensation expense (in dollars)	$ 850	$ 3,462