Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2016

Compensation Expense Related to Stock-Based Compensation Plans

The compensation 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 March 31,
	Three months ended March 31,
	2016			2015
Cost of sales	$	235		$	237
Research and development	297			17
Sales and marketing	(63		)	502
General and administrative	1,511			1,312
Total stock-based compensation expense	$	1,980		$	2,068

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.



	Three months ended March 31,
	Three months ended March 31,
	2016		2015
Risk-free interest rate	1.46	%	1.45	%
Expected option life (in years)	6.46		6.22
Volatility rate	36	%	40	%
Dividend rate	—	%	—	%