Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of non-cash stock-based compensation expense

Non-cash stock-based compensation expense (employee stock purchase plan and service-based stock options) is summarized in the following table: 

	Three Months Ended March 31,
(In thousands)	2018		2017
Cost of goods sold	$	142	$	91
Research and development	475		58
Selling, general and administrative	725		353
Total non-cash stock-based compensation expense	$	1,342	$	502

Schedule of weighted average assumptions used to estimate fair value of each service-based stock option grant

The fair value of each service-based stock option grant for the reported periods is estimated on the date of the grant using the Black-Scholes option-pricing model using the weighted average assumptions noted in the following table.

	Three Months Ended March 31,
Service-Based Stock Options	2018		2017
Expected dividend rate	—	%	—	%
Expected stock price volatility	82.3 – 84.4%		81.3 – 88.2%
Risk-free interest rate	2.4 – 2.8%		2 – 2.3%
Expected life (years)	6.1 – 6.3		6.1 – 6.3