Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2020

Equity [Abstract]

Share-based Payment Arrangement, Option, Activity

A summary of the status of stock option activity for the three months ended March 31, 2020 is as follows (in thousands, except price data):

	Shares	Weighted-average exercise price per share
Outstanding at December 31, 2019	944	$	30.63
Granted	121	77.16
Exercised	(65)	21.26
Forfeited	(12)	43.34
Outstanding at March 31, 2020	988	$	36.77

Schedule of Nonvested Share Activity

A summary of the status of restricted stock unit activity for the three months ended March 31, 2020 is as follows (in thousands, except price data):

	Shares	Weighted-average grant date fair value
Non-vested December 31, 2019	786	$	41.88
Granted	186	77.53
Vested	(60)	18.21
Forfeited	(17)	49.85
Non-vested at March 31, 2020	895	$	50.74

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 Income was as follows (in thousands):

	Three Months Ended March 31,
	2020		2019
Cost of sales	$	258	$	280
Research and development	642		565
Sales and marketing	1,297		1,119
General and administrative	1,681		1,624
Total stock-based compensation expense	$	3,878	$	3,588

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,
	2020			2019
Risk-free interest rate	1.35		%	2.51		%
Expected option life (in years)	5.14			5.68
Volatility rate	39		%	39		%
Dividend rate	0		%	0		%
Weighted-average grant date fair value	$	28.24		$	23.67