Stock-Based Compensation Expense (Tables)

3 Months Ended

Mar. 31, 2019

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

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs

The stock-based compensation expense before income tax expense for the three months ended March 31, 2019 and 2018, consisted of the following (in thousands):

	Three Months Ended March 31,
	2019		2018
Cost of sales	$	252	$	184
Research and development	192		124
Selling, general and administrative	1,322		948
Stock-based compensation expense before taxes	$	1,766	$	1,256

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

In applying the Black-Scholes methodology to the option grants, the fair value of our stock-based awards granted was estimated using the following assumptions for the periods indicated below:

	Three Months Ended March 31,
	2019	2018
Risk-free interest rate	2.42% - 2.56%	2.63%
Expected option term	3.0 - 5.0 years	5.0 years
Expected dividend yield	—	—
Expected price volatility	28.93% - 33.69%	34.32%