Stock Plans (Tables)

3 Months Ended

Mar. 31, 2017

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

Schedule of Stock Compensation Expense

Stock compensation expense is as follows:

	Three Months Ended March 31,
(In thousands)	2017		2016
Stock compensation expense	$	6,325	$	5,498
Income tax benefit	2,386		2,132
Stock compensation expense, net of income tax benefit	$	3,939	$	3,366

Summary of Stock Option Activity

A summary of stock option activity for the three months ended March 31, 2017 follows:

	Shares		Weighted Average Exercise Price
Outstanding at January 1, 2017	1,576,092		$	37.63
Exercised	(175,953	)	35.61
Outstanding at March 31, 2017	1,400,139		37.89
Exercisable at March 31, 2017	1,032,135		$	34.94

Summary of Restricted Stock and Unit Activity

A summary of restricted stock and unit activity for the three months ended March 31, 2017 follows:

	Shares		Weighted Average Grant Date Fair Value
Unvested at January 1, 2017	234,592		$	49.76
Granted	37,048		72.25
Vested	(58,503	)	51.18
Forfeited	(1,166	)	48.87
Unvested at March 31, 2017	211,971		$	53.82

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 2017 with a market condition modifier.

Fair value per unit	$72.28
Risk-free interest rate	1.45%
Expected dividend yield	2.31%
Expected volatility	29.1%
MSA stock beta	1.272

Summary of Performance Stock Unit Activity

A summary of performance stock unit activity for the three months ended March 31, 2017 follows:

	Shares		Weighted Average Grant Date Fair Value
Unvested at January 1, 2017	186,621		$	46.18
Granted	92,580		72.28
Performance adjustments	28,215		57.42
Vested	(70,403	)	57.27
Unvested at March 31, 2017	237,013		$	54.42