Stock-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation Expense

Total stock-based compensation expense was as follows:

	Year Ended December 31,
	2019		2018		2017
	(In thousands)
Employees:
Restricted stock and performance shares	$	20,182	$	12,559	$	11,566
Stock options		4,032		2,193		1,882
		24,214		14,752		13,448
Non-employee directors:
Restricted stock		1,080		1,098		973
Total stock-based compensation	$	25,294	$	15,850	$	14,421

Assumptions Used for the Black-Scholes Option-Pricing Model to Determine the Per Share Weighted Average Fair Value for Options Granted

The following table represents the assumptions used for the Black-Scholes option-pricing model to determine the per share weighted-average fair value for options granted, excluding the two awards discussed below:

	Year Ended December 31,
	2019			2018			2017
Expected life (years)		5.0			5.0			5.0
Risk-free interest rate		2.6	%		2.2	%		1.9	%
Expected volatility		25.9	%		26.9	%		28.0	%
Expected dividend yield		0.8	%		0.8	%		0.8	%

Stock Option Activity

The following table reports stock option activity during the three years ended December 31, 2019 and the intrinsic value as of December 31, 2019:

	Number of Shares			Weighted-Average Exercise Price ($)		Remaining Contractual Term		Intrinsic Value ($)
								(In thousands)
Outstanding at December 31, 2016		855,740		$	36.80
Granted		54,838			156.85
Canceled		—			—
Exercised		(380,967	)		11.26
Outstanding at December 31, 2017		529,611			67.60
Granted		168,217			261.19
Canceled		(1,676	)		142.69
Exercised		(120,588	)		24.66
Outstanding at December 31, 2018		575,564			132.93
Granted		82,474			279.57
Canceled		(548	)		198.67
Exercised		(106,899	)		28.24			$	33,639
Outstanding at December 31, 2019		550,591			175.16		2.8		112,294
Exercisable at December 31, 2019		171,782			96.71		1.5		48,512

Summary of Performance of Share Activity for Annual Awards

The following table reports performance share activity for annual awards for the three years ended December 31, 2019:

Performance year:	2019		2018		2017
Target share pay-out		16,716		10,479		12,971
Actual share pay-out (paid in following year)		19,400		10,479		8,094
Weighted average fair value per share on grant date	$	223.81	$	202.04	$	155.53

Restricted Stock and Performance Share Activity

The following table reports restricted stock and performance share activity during the three years ended December 31, 2019:

	Number of Restricted Shares			Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2016		383,978		$	71.50
Granted		61,434
Performance share pay-out		21,422
Canceled		(4,590	)
Vested		(142,645	)
Outstanding at December 31, 2017		319,599		$	88.77
Granted		59,179
Performance share pay-out		8,094
Canceled		(4,046	)
Vested		(110,956	)
Outstanding at December 31, 2018		271,870		$	112.47
Granted		118,632
Performance share pay-out		87,163
Canceled		(2,321	)
Vested		(129,312	)
Outstanding at December 31, 2019		346,032		$	154.27