Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Stock-based Compensation Expense and Related Income Tax Benefit

Stock-based compensation expense by statement of operations caption and the related income tax benefit were as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
(In thousands)	2021		2020		2021		2020
Cost of sales	$	40	$	36	$	77	$	110
Research and development expenses	318		288		631		524
Selling, general and administrative expenses:
Employees	1,705		1,557		3,573		3,140
Outside directors	381		410		763		820
Total employee and director stock-based compensation expense	$	2,444	$	2,291	$	5,044	$	4,594
Income tax benefit	$	416	$	500	$	882	$	1,006

Stock Option Activity

Stock option activity was as follows:    

	Number of Options (in thousands)	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2020	774	$	43.01
Granted	80	59.43
Exercised	(22)	44.39			$	253
Forfeited/canceled/expired	—	—
Outstanding at June 30, 2021 (1)	832	$	44.56	3.54	$	7,083
Vested and expected to vest at June 30, 2021 (1)	832	$	44.56	3.54	$	7,083
Exercisable at June 30, 2021 (1)	638	$	43.39	2.77	$	6,128

(1)The aggregate intrinsic value represents the total pre-tax value (the difference between our closing stock price on the last trading day of the second quarter of 2021 and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had they all exercised their options on June 30, 2021. This amount will change based on the fair market value of our stock.

Assumptions Used in Valuation and Weighted Average Fair Value of Stock Option Grants

The assumptions we utilized in the Black-Scholes option pricing model and the resulting weighted average fair value of stock option grants were the following:

	Three Months Ended June 30,						Six Months Ended June 30,
	2021			2020			2021			2020
Weighted average fair value of grants	$	—		$	—		$	23.97		$	17.70
Risk-free interest rate	—		%	—		%	0.41		%	1.44		%
Expected volatility	—		%	—		%	48.49		%	43.95		%
Expected life in years	0.00			0.00			4.62			4.59

Non-Vested Restricted Stock Award Activity

Non-vested restricted stock award activity was as follows:

	Shares (in thousands)		Weighted-Average Grant Date Fair Value
Non-vested at December 31, 2020	$	374	$	34.53
Granted	123		59.43
Vested	(177)		35.41
Forfeited	(7)		38.08
Non-vested at June 30, 2021	$	313	$	43.74