Stock Plans (Tables)

9 Months Ended

Sep. 30, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Stock Compensation Expense

Stock compensation expense is as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
(In thousands)	2018		2017		2018		2017
Stock compensation expense	$	1,904	$	1,435	$	9,595	$	9,668
Income tax benefit	463		543		2,332		3,650
Stock compensation expense, net of income tax benefit	$	1,441	$	892	$	7,263	$	6,018

Summary of Stock Option Activity

A summary of stock option activity for the nine months ended September 30, 2018, follows:

	Shares		Weighted Average Exercise Price
Outstanding at January 1, 2018	955,446		$	42.75
Exercised	(160,617	)	38.31
Forfeited	(4,721	)	44.50
Outstanding at September 30, 2018	790,108		43.66
Exercisable at September 30, 2018	692,773		$	43.55

Summary of Restricted Stock and Unit Activity

A summary of restricted stock and unit activity for the nine months ended September 30, 2018, follows:

	Shares		Weighted Average Grant Date Fair Value
Unvested at January 1, 2018	227,161		$	57.50
Granted	73,062		87.00
Vested	(88,298	)	58.18
Forfeited	(4,661	)	58.94
Unvested at September 30, 2018	207,264		$	68.76

Schedule of Fair Value Assumptions for Units

The following weighted average assumptions were used in the Monte Carlo model for units granted in the first quarter of 2018 with a market condition modifier.

Fair value per unit	$83.58
Risk-free interest rate	2.36%
Expected dividend yield	1.82%
Expected volatility	28.3%
MSA stock beta	1.240

Summary of Performance Stock Unit Activity

A summary of performance stock unit activity for the nine months ended September 30, 2018, follows:

	Shares		Weighted Average Grant Date Fair Value
Unvested at January 1, 2018	242,186		$	55.06
Granted	62,775		84.79
Performance adjustments	(3,356	)	44.61
Vested	(41,660	)	40.23
Forfeited	(8,659	)	44.53
Unvested at September 30, 2018	251,286		$	65.45