Stock-Based Compensation Expense (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [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 and six months ended June 30, 2019 and 2018 consisted of the following (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2019		2018		2019		2018
Cost of sales	$	355	$	232	$	607	$	416
Research and development	281		147		473		271
Selling, general and administrative	1,887		1,186		3,209		2,134
Stock-based compensation expense before taxes	$	2,523	$	1,565	$	4,289	$	2,821

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:

	Six Months Ended June 30,
	2019	2018
Risk-free interest rate	1.90% - 2.56%	2.63% - 2.77%
Expected option term	3.0 - 5.0 years	5.0 years
Expected dividend yield	—	—
Expected price volatility	28.66% - 33.69%	34.06% - 34.32%