Stock-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation Expense

Total stock-based compensation expense was as follows:

	Year Ended December 31,
	2018		2017		2016
	(In thousands)
Employees:
Restricted stock and performance shares	$	12,559	$	11,566	$	12,459
Stock options		2,193		1,882		1,143
		14,752		13,448		13,602
Non-employee directors:
Restricted stock		1,098		973		909
Total stock-based compensation	$	15,850	$	14,421	$	14,511

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 for the three years ended December 31, 2018:

	2018			2017			2016
Expected life (years)		5.0			5.0			6.0
Risk-free interest rate		2.2	%		1.9	%		1.9	%
Expected volatility		26.9	%		28.0	%		33.0	%
Expected dividend yield		0.8	%		0.8	%		1.0	%

Stock Option Activity

The following table reports stock option activity during the three years ended December 31, 2018 and the intrinsic value as of December 31, 2018:

	Number of Shares			Weighted-Average Exercise Price ($)		Remaining Contractual Term		Intrinsic Value ($)
								(In thousands)
Outstanding at December 31, 2015		939,036		$	23.83
Granted		112,988			102.40
Canceled		(874	)		101.77
Exercised		(195,410	)		12.35
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			$	21,823
Outstanding at December 31, 2018		575,564			132.93		3.2		53,651
Exercisable at December 31, 2018		203,564			53.49		2.1		32,126

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, 2018:

Performance year:	2018		2017		2016
Share pay-out plan		10,479		12,971		15,390
Actual share pay-out in following year		10,479		8,094		21,423
Weighted average fair value per share on grant date	$	202.04	$	155.53	$	101.77

Restricted Stock and Performance Share Activity

The following table reports restricted stock and performance share activity during the three years ended December 31, 2018:

	Number of Restricted Shares			Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2015		432,138		$	56.24
Granted		95,419
Performance share pay-out		61,936
Canceled		(12,786	)
Vested		(192,729	)
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