Stock-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation Expense

Total stock-based compensation expense was as follows:

	Year Ended December 31,
	2017		2016		2015
	(In thousands)
Employees:
Restricted stock and performance shares	$	11,566	$	12,459	$	10,792
Stock options		1,882		1,143		826
		13,448		13,602		11,618
Non-employee directors:
Restricted stock		973		909		901
Total stock-based compensation	$	14,421	$	14,511	$	12,519

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, 2017:

	2017			2016			2015
Expected life (years)		5.0			6.0			7.0
Risk-free interest rate		1.9	%		1.9	%		1.9	%
Expected volatility		28.0	%		33.0	%		56.7	%
Expected dividend yield		0.8	%		1.0	%		1.1	%

Stock Option Activity

The following table reports stock option activity during the three years ended December 31, 2017 and the intrinsic value as of December 31, 2017:

	Number of Shares			Weighted-Average Exercise Price ($)		Remaining Contractual Term		Intrinsic Value ($)
								(In thousands)
Outstanding at December 31, 2014		1,014,420		$	13.81
Granted		120,650			88.15
Canceled		—			—
Exercised		(196,034	)		11.60
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			$	68,068
Outstanding at December 31, 2017		529,611			67.60		3.3		71,046
Exercisable at December 31, 2017		254,079			24.61		3.0		45,009

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, 2017:

Performance year:	2017		2016		2015
Share pay-out plan		12,971		15,390		28,520
Actual share pay-out in following year		8,094		21,423		37,696
Weighted average fair value per share on grant date	$	155.53	$	101.77	$	70.60

Restricted Stock and Performance Share Activity

The following table reports restricted stock and performance share activity during the three years ended December 31, 2017:

	Number of Restricted Shares			Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2014		435,989		$	41.83
Granted		117,668
Performance share pay-out		117,647
Canceled		(3,845	)
Vested		(235,321	)
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