Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Recent Share-Based Compensation Expense

The following is a summary of share-based compensation expense:



Year	Share-Based Compensation Expense		Tax Benefit
2016	$	39.2	$	15.1
2017	40.4		13.6
2018	44.7		11.2

Schedule of Transactions of the Company's Stock Options

The following table summarizes the transactions in the Company’s stock options:



	Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)
Unexercised options outstanding—December 31, 2017	0.6		$	122.04
Options granted	0.0		179.54
Options exercised	(0.1	)	99.57
Options forfeited	(0.0	)	122.40
Unexercised options outstanding—December 31, 2018	0.5		130.81		3.7
Exercisable at December 31, 2018	0.1		138.97		2.3

Schedule of Assumptions Used to Determine Fair Value of Options Granted

The fair value of options granted was estimated using the Black-Scholes option pricing model and were $39.02, $48.05 and $48.64, per option, for the years ended December 31, 2016, 2017 and 2018, respectively. The weighted average grant date assumptions used to estimate the fair value of options granted were as follows:



	For the Years Ended December 31,
	2016		2017		2018
Dividend yield	0.0	%	0.5	%	0.8	%
Expected volatility⁽¹⁾	30.7	%	28.0	%	25.5	%
Risk-free interest rate⁽²⁾	1.6	%	2.1	%	2.8	%
Expected life of options (in years)⁽³⁾	5.7		5.7		5.7
Forfeiture rate	0.0	%	0.0	%	0.0	%

__________________________


⁽¹⁾	Expected volatility is based on historical and implied volatility.


⁽²⁾	Risk-free interest rate is based on the U.S. Treasury yield curve in effect at the date of grant.


⁽³⁾	Expected life of options (in years) is based on the Company’s historical and expected exercise behavior.

Schedule of Transactions of the Company's Restricted Stock

The following table summarizes the transactions in the Company’s restricted stock units:



	Restricted Stock		Weighted Average Grant Date Value
Unvested units—December 31, 2017	0.4		$	162.32
Units granted	0.2		201.75
Units vested	(0.0	)	188.93
Units forfeited	(0.0	)	154.92
Unvested units—December 31, 2018	0.6		172.74