Stock Award Plans (Tables)

12 Months Ended

Dec. 31, 2017

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Compensation Cost Breakdown in Statement of Earnings

The Company has share-based compensation plans which are described below. The compensation cost that has been charged against earnings for the Company’s stock award plans and the income tax benefit recognized in the statement of earnings for stock awards for the years ended December 31, 2017, 2016 and 2015 were as follows (in thousands):

	2017		2016		2015
Compensation cost	$	11,460	$	11,675	$	11,104
Income tax benefit	$	4,333	$	4,378	$	4,120

Summary of Stock Option Valuation Assumptions

The key input variables used in valuing the stock options during the years ended December 31, 2017, 2016 and 2015 were as follows:

	2017			2016			2015
Dividend yield	None			None			None
Average risk-free interest rate		2.0	%		1.5	%		1.3	%
Stock price volatility		27	%		30	%		33	%
Estimated option term	Six years			Six years			Six years

Employee Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Stock Option Activity

The following is a summary of the stock option activity under the employee plan described above for the years ended December 31, 2017, 2016 and 2015:

	Outstanding Non- Qualified or Nonincentive Stock Awards			Weighted Average Exercise Price
Outstanding at December 31, 2014		322,956		$	69.95
Granted		114,894		$	74.99
Canceled or expired		(7,418	)	$	86.28
Outstanding at December 31, 2015		430,432		$	71.01
Granted		186,706		$	53.50
Canceled or expired		(16,017	)	$	80.17
Outstanding at December 31, 2016		601,121		$	65.33
Granted		123,141		$	68.46
Exercised		(36,616	)	$	47.95
Canceled or expired		(32,991	)	$	74.07
Outstanding at December 31, 2017		654,655		$	66.45

Summary of Outstanding and Exercisable Stock Options

The following table summarizes information about the Company’s outstanding and exercisable stock options under the employee plan at December 31, 2017:

		Options Outstanding								Options Exercisable
Range of Exercise Prices		Number Outstanding		Weighted Average Remaining Contractual Life in Years		Weighted Average Exercise Price		Aggregated Intrinsic Value		Number Exercisable		Weighted Average Exercise Price		Aggregated Intrinsic Value
$	46.74 – $51.23		197,776		3.8	$	50.02				100,806	$	48.86
$	64.65 – $74.99		394,704		4.0	$	69.68				217,627	$	70.25
$	93.64 – $96.85		33,987		3.1	$	94.31				33,987	$	94.31
$	101.46 – $104.37		28,188		3.2	$	102.88				28,188	$	102.88
$	46.74 – $104.37		654,655		3.8	$	66.45	$	3,455,000		380,608	$	69.15	$	1,883,000

Summary of Restricted Stock Award Activity

The following is a summary of the restricted stock award activity under the employee plan described above for the years ended December 31, 2017, 2016 and 2015:

	Unvested Restricted Stock Award Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested balance at December 31, 2014		321,453		$	71.04
Granted		122,740		$	75.04
Vested		(113,958	)	$	60.73
Forfeited		(18,508	)	$	82.00
Nonvested balance at December 31, 2015		311,727		$	75.73
Granted		190,610		$	53.56
Vested		(105,109	)	$	69.93
Forfeited		(19,573	)	$	76.06
Nonvested balance at December 31, 2016		377,655		$	66.14
Granted		127,255		$	68.50
Vested		(105,600	)	$	68.91
Forfeited		(35,189	)	$	69.45
Nonvested balance at December 31, 2017		364,121		$	65.84

Director Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Stock Option Activity

The following is a summary of the stock option activity under the director plan described above for the years ended December 31, 2017, 2016, and 2015:

	Outstanding Non- Qualified or Nonincentive Stock Awards			Weighted Average Exercise Price
Outstanding at December 31, 2014		298,334		$	60.01
Exercised		(77,905	)	$	47.65
Outstanding at December 31, 2015		220,429		$	64.37
Exercised		(9,000	)	$	35.72
Canceled or expired		(6,000	)	$	99.52
Outstanding at December 31, 2016		205,429		$	64.60
Granted		3,188		$	70.65
Exercised		(39,000	)	$	46.23
Canceled or expired		(12,000	)	$	87.35
Outstanding at December 31, 2017		157,617		$	67.54

Summary of Outstanding and Exercisable Stock Options

The following table summarizes information about the Company’s outstanding and exercisable stock options under the director plan at December 31, 2017:

		Options Outstanding								Options Exercisable
Range of Exercise Prices		Number Outstanding		Weighted Average Remaining Contractual Life in Years		Weighted Average Exercise Price		Aggregate Intrinsic Value		Number Exercisable		Weighted Average Exercise Price		Aggregate Intrinsic Value
$	29.60		6,000		1.3	$	29.60				6,000	$	29.60
$	41.24 – $56.45		53,276		2.4	$	52.77				53,276	$	52.77
$	61.89 – $62.48		35,153		4.5	$	62.31				35,153	$	62.31
$	70.65 – $99.52		63,188		6.0	$	86.50				62,391	$	86.71
$	29.60 – $99.52		157,617		4.3	$	67.54	$	1,128,000		156,820	$	67.52	$	1,128,000

Summary of Restricted Stock Award Activity

The following is a summary of the restricted stock award activity under the director plan described above for the years ended December 31, 2017, 2016 and 2015:

	Unvested Restricted Stock Award Shares			Weighted Average Grant Date Fair Value Per Share
Nonvested balance at December 31, 2014		292		$	99.52
Granted		20,350		$	78.52
Vested		(18,851	)	$	79.77
Nonvested balance at December 31, 2015		1,791		$	68.73
Granted		23,074		$	64.89
Vested		(24,518	)	$	65.17
Nonvested balance at December 31, 2016		347		$	64.89
Granted		21,198		$	70.65
Vested		(21,226	)	$	70.56
Nonvested balance at December 31, 2017		319		$	70.65