Stock-based Compensation - Non-cash 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
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	$ 3,285	$ 1,932	$ 10,095	$ 5,739
Cost of goods sold
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	543	284	1,519	820
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	583	365	1,993	1,282
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Non-cash stock-based compensation expense	$ 2,159	$ 1,283	$ 6,583	$ 3,637