Stock-Based Compensation - Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee and non-employee stock options
Stock based compensation expense
Options granted (in shares)	2,319,000
Stock-based compensation expense	$ 14,198	$ 11,402	$ 10,601
Unrecognized compensation expense	$ 24,800
Unrecognized compensation expense recognized over weighted average period	2 years 5 months 12 days
Employee and non-employee stock options | Cost of product revenues
Stock based compensation expense
Stock-based compensation expense	$ 569	544	641
Employee and non-employee stock options | Research and development
Stock based compensation expense
Stock-based compensation expense	4,043	3,214	2,853
Employee and non-employee stock options | Selling, general and administrative
Stock based compensation expense
Stock-based compensation expense	9,586	7,644	7,107
Employee stock options
Stock based compensation expense
Stock-based compensation expense	14,081	11,402	10,317
Employee stock options | Cost of product revenues
Stock based compensation expense
Stock-based compensation expense	564	544	651
Employee stock options | Research and development
Stock based compensation expense
Stock-based compensation expense	4,043	3,214	2,829
Employee stock options | Selling, general and administrative
Stock based compensation expense
Stock-based compensation expense	$ 9,474	$ 7,644	6,837
Non-employee stock options
Stock based compensation expense
Options granted (in shares)	131,865
Options unvested (in shares)	36,344
Stock-based compensation expense	$ 117		284
Non-employee stock options | Cost of product revenues
Stock based compensation expense
Stock-based compensation expense	5		(10)
Non-employee stock options | Research and development
Stock based compensation expense
Stock-based compensation expense			24
Non-employee stock options | Selling, general and administrative
Stock based compensation expense
Stock-based compensation expense	$ 112		$ 270