Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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

Summary of Recent Share-Based Compensation Expense

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



Period	Share-Based Compensation Expense		Tax Benefit
2013	$	27.5	$	10.6
2014	29.3		11.3
2015	34.2		13.2

Schedule of Transactions of the Company's Stock Options

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



	Stock Options		Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (years)
Unexercised options outstanding—January 1, 2015	2.3		$	83.42
Options granted	0.0		207.61
Options exercised	(0.9	)	65.95
Options forfeited	(0.0	)	101.29
Unexercised options outstanding—December 31, 2015	1.4		96.18		2.2
Exercisable at December 31, 2015	1.3		94.43		2.1

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. The weighted average fair value of options granted during the years ended December 31, 2013, 2014 and 2015 was $61.82, $60.20, and $54.92 per option, respectively, based on the weighted-average grant date assumptions stated below.



	For the Years Ended December 31,
	2013		2014		2015
Dividend yield	0.0	%	0.0	%	0.0	%
Expected volatility⁽¹⁾	34.4	%	29.7	%	26.7	%
Risk-free interest rate⁽²⁾	1.5	%	1.8	%	1.5	%
Expected life of options (in years)⁽³⁾	5.0		5.0		5.0
Forfeiture rate⁽³⁾	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 data and expected exercise behavior.

Summary of Transactions of the Company's Restricted Stock

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



	Restricted Stock		Weighted Average Grant Date Value
Unvested units—January 1, 2015	0.4		$	182.83
Units granted	0.3		197.59
Units vested	(0.1	)	174.19
Units forfeited	(0.0	)	190.23
Unvested units—December 31, 2015	0.6		192.04