Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Fair Value Assumptions for Stock Options

The following are the weighted-average assumptions used to calculate the grant-date fair values of stock option awards granted in the years ended December 31, 2017, 2016 and 2015:

	For the Years Ended December 31
	2017	2016	2015
Expected dividend yield	1.39%	1.45%	1.53%
Expected volatility	30.01%	35.62%	40.32%
Expected term	7.2 years	7.3 years	7.3 years
Risk-free interest rate	2.22%	1.52%	1.96%

Summary of Stock Option Activity

A summary of stock option activity for the year ended December 31, 2017 is presented below:

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate IntrinsicValue ($000)
Options
Outstanding at January 1, 2017		436,126		$	42.99
Granted		71,434			78.56
Exercised		(104,277	)		32.32
Forfeited		(11,478	)		50.78
Outstanding at December 31, 2017		391,805			52.09		6.33	$	10,532
Vested or expected to vest at December 31, 2017		384,777			51.95		6.29		10,396
Exercisable at December 31, 2017		230,118			47.62		4.77		7,214

Summary of Stock Award Activity

A summary of stock award activity for the year ended December 31, 2017, is presented below:

	Shares			Weighted-Average GrantDate Fair Value
Stock Awards
Unvested at January 1, 2017		256,766		$	40.74
Granted		40,171			75.94
Vested		(113,738	)		39.54
Forfeited		(14,166	)		45.93
Unvested at December 31, 2017		169,033

Summary of SARs Activity

The following is a summary of SARs activity for the year ended December 31, 2017:

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value ($000)
SARs
Outstanding at January 1, 2017		553,582		$	47.81
Granted		148,723			78.73
Exercised		(73,739	)		44.67
Forfeited		(11,916	)		68.95
Outstanding at December 31, 2017		616,650			55.23		7.46	$	14,640