Share-Based Compensation and Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2017

Restricted stock [Member]

Share-Based Compensation and Benefit Plans

Summary of activity of share-based compensation

	For the Three Months Ended   September 30,				For the Nine Months Ended   September 30,
	2017		2016		2017		2016
Compensation expense for shares issued under the ESPP	$	545	$	538	$	1,659	$	1,610
Income tax benefit from compensation expense related to shares issued under the ESPP	208		201		632		601
Compensation expense for restricted shares awarded	258		327		1,350		968
Income tax benefit from compensation expense related to restricted awards	$	98	$	122	$	515	$	361

Stock option [Member]

Share-Based Compensation and Benefit Plans

Summary of stock options

	Shares		Weighted-Average Exercise Price
Outstanding at December 31, 2016	2,800		$	104.90
Granted	240		257.39
Exercised	(483	)	51.35
Forfeited	(26	)	207.45
Outstanding at September 30, 2017	2,531		$	128.50
Exercisable at September 30, 2017	1,705		$	75.65

Black-Scholes option pricing model

	For the Nine Months Ended   September 30,
	2017		2016
Risk free interest rate	1.98	%	1.45	%
Expected life	5.5 Years		5.6 Years
Expected volatility	22.2	%	22.4	%
Expected dividend yield	—	%	—	%

Summary of activity of share-based compensation

	For the Three Months Ended   September 30,				For the Nine Months Ended   September 30,
	2017		2016		2017		2016
Compensation expense for stock options awarded	$	3,679	$	3,653	$	11,826	$	11,793
Income tax benefit from compensation expense related to stock options	1,402		1,365		4,507		4,405