Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2020

Equity [Abstract]

Share-based Payment Arrangement, Option, Activity

A summary of the status of stock option activity for the six months ended June 30, 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	122	77.54
Exercised	(220)	21.12
Forfeited	(12)	43.34
Outstanding at June 30, 2020	834	$	39.85

Schedule of Nonvested Share Activity

A summary of the status of restricted stock unit activity for the six months ended June 30, 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	202	85.34
Vested	(107)	26.07
Forfeited	(18)	58.11
Non-vested at June 30, 2020	863	$	53.71

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 June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Cost of sales	$	435	$	262	$	693	$	542
Research and development	866		544		1,508		1,109
Sales and marketing	1,341		904		2,638		2,023
General and administrative	2,488		1,662		4,169		3,286
Total stock-based compensation expense	$	5,130	$	3,372	$	9,008	$	6,960

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.

	Six Months Ended June 30,
	2020			2019
Risk-free interest rate	1.34		%	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	$	28.39		$	23.67