Stock-based Compensation - (Tables)

9 Months Ended

Sep. 30, 2019

Share-based Payment Arrangement [Abstract]

Schedule of non-cash stock-based compensation expense

Non-cash stock-based compensation expense (employee stock purchase plan, service-based stock options and restricted stock units) included in cost of goods sold, research and development expenses and selling, general and administrative expenses is summarized in the following table: 

	Three Months Ended September 30,				Nine Months Ended September 30,
(In thousands)	2019		2018		2019		2018
Cost of goods sold	$	543	$	284	$	1,519	$	820
Research and development	583		365		1,993		1,282
Selling, general and administrative	2,159		1,283		6,583		3,637
Total non-cash stock-based compensation expense	$	3,285	$	1,932	$	10,095	$	5,739

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.

	Nine Months Ended September 30,
Service-Based Stock Options	2019		2018
Expected dividend rate	—	%	—	%
Expected stock price volatility	79.5-85.5%		82.3-88.3%
Risk-free interest rate	1.4-2.7%		2.4-2.9%
Expected life (years)	5.3-6.3		5.3-6.3