Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2018

Equity [Abstract]

Compensation Expense Related to Stock-Based Compensation Plans

The expense related to the Company’s stock-based compensation plans included in the accompanying Consolidated Statements of Operations was as follows (in thousands):

	Three months ended September 30,				Nine months ended September 30,
	2018		2017		2018		2017
Cost of sales	$	255	$	117	$	751	$	354
Research and development	539		396		1,732		1,212
Sales and marketing	686		434		2,199		1,341
General and administrative	1,295		932		4,508		3,031
Total stock-based compensation expense	$	2,775	$	1,879	$	9,190	$	5,938

Estimated Fair Value of Each Stock Option Award

The estimated fair value of each stock option was determined on the date of grant using the Black-Scholes option valuation model with the following weighted-average assumptions for the option grants.

	Nine months ended September 30,
	2018		2017
Risk-free interest rate	2.49	%	2.31	%
Expected option life (in years)	6.29		6.63
Volatility rate	36	%	36	%
Dividend rate	—	%	—	%