Stock-Based Compensation Expense (Tables)

6 Months Ended

Jun. 30, 2018

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 and six months ended June 30, 2018 and 2017, consisted of the following (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Cost of sales	$	232	$	168	$	416	$	264
Research and development	147		100		271		152
Selling, general and administrative	1,186		846		2,134		1,275
Stock-based compensation expense before taxes	$	1,565	$	1,114	$	2,821	$	1,691

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,
	2018	2017
Risk-free interest rate	2.63% - 2.77%	1.77% - 1.79%
Expected option life	5.0 years	5.0 years
Expected dividend yield	—	—
Expected price volatility	34.06% - 34.32%	33.81% - 34.03%