Stock-based Compensation - Non-cash 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
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Non-cash stock-based compensation expense	$ 1,932	$ 755	$ 5,739	$ 2,053
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Non-cash stock-based compensation expense	284	119	820	316
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Non-cash stock-based compensation expense	365	177	1,282	391
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Non-cash stock-based compensation expense	$ 1,283	$ 459	$ 3,637	$ 1,346