Stock-Based Compensation - Non-cash Stock Compensation Expense (Details) - Employee stock purchase plan and service-based stock options - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock-based compensation expense	$ 7,223	$ 2,680	$ 2,499
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock-based compensation expense	1,015	428	427
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock-based compensation expense	1,672	506	497
General, selling and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total non-cash stock-based compensation expense	$ 4,536	$ 1,746	$ 1,575