Stock-Based Compensation Expense (Tables)

9 Months Ended

Sep. 30, 2018

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

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

Stock-based compensation expense before income tax expense for the three and nine months ended September 30, 2018 and 2017, consisted of the following (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2018		2017		2018		2017
Cost of sales	$	241	$	189	$	657	$	453
Research and development	141		110		412		262
Selling, general and administrative	1,291		893		3,425		2,168
Stock-based compensation expense before taxes	$	1,673	$	1,192	$	4,494	$	2,883

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:

	Nine Months Ended September 30,
	2018	2017
Risk-free interest rate	2.63% - 2.77%	1.77% - 1.83%
Expected option life	5.0 years	5.0 years
Expected dividend yield	—	—
Expected price volatility	34.06% - 34.32%	33.81% - 34.07%