Stock-Based Compensation - Compensation Expense (Details) - USD ($) $ in Thousands		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee and non-employee stock options
Stock based compensation expense
Options granted (in shares)		2,078,000
Stock-based compensation expense		$ 11,402	$ 10,601	$ 7,326
Unrecognized compensation expense	$ 20,000	$ 20,000
Unrecognized compensation expense recognized over weighted average period		2 years 6 months 7 days
Employee and non-employee stock options | Cost of product revenues
Stock based compensation expense
Stock-based compensation expense		$ 544	641	592
Employee and non-employee stock options | Research and development
Stock based compensation expense
Stock-based compensation expense		3,214	2,853	1,575
Employee and non-employee stock options | Selling, general and administrative
Stock based compensation expense
Stock-based compensation expense		7,644	7,107	5,159
Employee stock options
Stock based compensation expense
Stock-based compensation expense		11,402	10,317	6,910
Employee stock options | Cost of product revenues
Stock based compensation expense
Stock-based compensation expense		544	651	351
Employee stock options | Research and development
Stock based compensation expense
Stock-based compensation expense		3,214	2,829	1,566
Employee stock options | Selling, general and administrative
Stock based compensation expense
Stock-based compensation expense		$ 7,644	6,837	4,993
Non-employee stock options
Stock based compensation expense
Options granted (in shares)	135,746
Options unvested (in shares)	3,401	3,401
Stock-based compensation expense			284	416
Non-employee stock options | Cost of product revenues
Stock based compensation expense
Stock-based compensation expense			(10)	241
Non-employee stock options | Research and development
Stock based compensation expense
Stock-based compensation expense			24	9
Non-employee stock options | Selling, general and administrative
Stock based compensation expense
Stock-based compensation expense			$ 270	$ 166