Stock Plans (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Stock Compensation Expense

Stock compensation expense is as follows:

	Three Months Ended September 30,					Nine Months Ended September 30,
(In thousands)	2021		2020			2021		2020
Stock compensation expense (benefit)	$	2,867	$	(1,309)	(a)	$	13,562	$	3,042
Income tax expense (benefit)	691		(319)			3,269		742
Stock compensation expense (benefit), net of tax	$	2,176	$	(990)		$	10,293	$	2,300

(a) The Company adjusted cumulative stock compensation expense for changes in expected performance against target metrics for unvested performance stock units. This resulted in a benefit during the three months ended September 30, 2020.

Summary of Stock Option Activity

A summary of stock option activity for the nine months ended September 30, 2021, follows:

	Shares	Weighted Average Exercise Price
Outstanding at January 1, 2021	283,998	$	46.23
Exercised	(58,234)	45.84
Forfeited	(210)	43.75
Outstanding at September 30, 2021	225,554	46.34
Exercisable at September 30, 2021	224,980	$	46.33

Summary of Restricted Stock and Unit Activity

A summary of restricted stock activity for the nine months ended September 30, 2021, follows:

	Shares	Weighted Average Grant Date Fair Value
Unvested at January 1, 2021	146,191	$	105.83
Granted	40,066	152.91
Vested	(62,155)	94.88
Forfeited	(3,502)	133.92
Unvested at September 30, 2021	120,600	$	126.30

Schedule of Fair Value Assumptions for Units

The following weighted average assumptions were used in estimating the fair value of the performance stock units granted in the first quarter of 2021.

Fair value per unit	$177.50
Risk-free interest rate	0.2%
Expected dividend yield	1.33%
Expected volatility	35.6%
MSA stock beta	0.932

Summary of Performance Stock Unit Activity

A summary of performance stock unit activity for the nine months ended September 30, 2021, follows:

	Shares	Weighted Average Grant Date Fair Value
Unvested at January 1, 2021	200,212	$	104.69
Granted	52,309	175.59
Performance adjustments	5,357	88.45
Vested	(64,543)	85.41
Unvested at September 30, 2021	193,335	$	129.86