Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Share-Based Compensation

Schedule of stock option activity

	Year Ended December 31,
	2017			2016			2015
		Weighted			Weighted			Weighted
		Average			Average			Average
		Exercise			Exercise			Exercise
	Shares	Price		Shares	Price		Shares	Price
Outstanding at January 1, 2017	246,535	$	42.53	285,405	$	38.85	294,342	$	35.91
Granted	33,634		91.23	25,682		63.79	26,430		61.74
Exercised	(59,480)		33.03	(63,527)		34.70	(35,360)		31.51
Forfeited	(2,000)		26.01	(1,025)		35.20	—		—
Expired	—		—	—		—	(7)		31.72
Outstanding at December 31, 2017	218,689		52.75	246,535		42.53	285,405		38.85
Exercisable at December 31, 2017	148,702		41.62	185,758		36.33	227,130		34.48
Weighted-average fair value of options granted during the year		$	35.42		$	25.19		$	25.08

Schedule of information pertaining to options outstanding

					Options Outstanding					Options Exercisable
						Weighted							Weighted
						Average							Average
						Remaining		Weighted			Weighted		Remaining
Range of					Number	Contractual		Average		Number	Average		Contractual
Exercise Prices					Outstanding	Life		Exercise Price		Outstanding	Exercise Price		Life
$	26.01	-	$	30.00	15,796	1.4	years	$	27.60	15,795	$	27.60
$	30.01	-	$	35.00	58,790	3.2	years	$	31.82	58,787	$	31.82
$	35.01	-	$	40.00	11,353	2.1	years	$	35.20	11,351	$	35.20
$	40.01	-	$	45.00	24,507	4.9	years	$	41.42	24,507	$	41.42
$	45.01	-	$	91.35	108,243	7.7	years	$	72.19	38,262	$	64.50
					218,689	5.4	years	$	52.75	148,702	$	41.62	4.1	years

Schedule of weighted-average assumptions used in valuing options

	Year ended December 31,
	2017		2016		2015
Dividend yield	1.40	%	1.60	%	1.4	%
Expected life	8.5	years	8.5	years	8.5	years
Expected volatility	37.2	%	40.6	%	40.9	%
Risk-free interest rate	2.43	%	1.90	%	1.79	%

Summary of nonvested restricted stock

		Weighted-
		Average
		Grant-Date
Restricted Stock	Shares	Fair Value
Nonvested at January 1, 2017	183,014	$	51.88
Granted	26,053		89.11
Vested	(61,950)		47.94
Forfeited	(4,425)		75.59
Nonvested at December 31, 2017	142,692		59.66

Vesting schedule of shares

	Shares
2017	37,713
2018	34,337
2019	51,940
2020	3,905
2021	3,405
Thereafter	11,392
	142,692

Summary of nonvested RSUs

		Weighted-
		Average
		Grant-Date
Restricted Stock Units	Shares	Fair Value
Nonvested at January 1, 2017	107,876	$	66.37
Granted	77,301		89.43
Vested	(39,672)		68.31
Forfeited	(1,518)		78.68
LTIP Adjustment	(3,951)		63.93
Nonvested at December 31, 2017	140,036		78.49