Share-Based Compensation and Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2019

Restricted stock [Member]

Share-Based Compensation and Benefit Plans

Summary of activity of share-based compensation

	For the Three Months Ended   June 30,				For the Six Months Ended   June 30,
	2019		2018		2019		2018
Compensation expense for shares issued under the ESPP	$	632	$	577	$	1,209	$	1,120
Income tax benefit from compensation expense related to shares issued under the ESPP	157		143		301		279
Compensation expense for restricted shares awarded	348		351		687		692
Income tax benefit from compensation expense related to restricted awards	$	86	$	87	$	171	$	172

Stock option [Member]

Share-Based Compensation and Benefit Plans

Summary of stock options

	Shares		Weighted-Average Exercise Price
Outstanding at December 31, 2018	1,860		$	178.57
Granted	164		360.45
Exercised	(181	)	109.99
Forfeited	(16	)	259.07
Outstanding at June 30, 2019	1,827		$	200.97
Exercisable at June 30, 2019	1,208		$	157.02

Black-Scholes option pricing model

	For the Six Months Ended   June 30,
	2019		2018
Risk free interest rate	2.44	%	2.59	%
Expected life	6.0 Years		6.1 Years
Expected volatility	25.0	%	23.8	%
Expected dividend yield	—	%	—	%

Summary of activity of share-based compensation

	For the Three Months Ended   June 30,				For the Six Months Ended   June 30,
	2019		2018		2019		2018
Compensation expense for stock options awarded	$	4,611	$	4,048	$	9,119	$	8,340
Income tax benefit from compensation expense related to stock options	1,146		1,008		2,267		2,076