Stock-Based Compensation - Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Stock based compensation expense
Stock based compensation expense	$ 2,986	$ 2,673	$ 8,406	$ 7,965
Cost of product revenues
Stock based compensation expense
Stock based compensation expense	147	160	430	482
Research and development
Stock based compensation expense
Stock based compensation expense	943	783	2,323	2,104
Selling, general and administrative
Stock based compensation expense
Stock based compensation expense	1,896	1,730	$ 5,653	5,379
Employee and non-employee stock options
Stock based compensation expense
Options granted (in shares)			1,921,000
Unrecognized compensation expense	21,300		$ 21,300
Unrecognized compensation expense recognized over weighted average period			2 years 8 months 12 days
Employee stock options
Stock based compensation expense
Stock based compensation expense	2,975	2,664	$ 8,393	7,701
Employee stock options | Cost of product revenues
Stock based compensation expense
Stock based compensation expense	138	164	420	479
Employee stock options | Research and development
Stock based compensation expense
Stock based compensation expense	943	784	2,323	2,105
Employee stock options | Selling, general and administrative
Stock based compensation expense
Stock based compensation expense	$ 1,894	1,716	$ 5,650	5,117
Non-employee stock options
Stock based compensation expense
Options granted (in shares)			136,046
Options unvested (in shares)	5,166		5,166
Stock based compensation expense	$ 11	9	$ 13	264
Non-employee stock options | Cost of product revenues
Stock based compensation expense
Stock based compensation expense	9	(4)	10	3
Non-employee stock options | Research and development
Stock based compensation expense
Stock based compensation expense		(1)		(1)
Non-employee stock options | Selling, general and administrative
Stock based compensation expense
Stock based compensation expense	$ 2	$ 14	$ 3	$ 262