Share-Based Compensation

3 Months Ended

Mar. 31, 2016

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

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



	For the Three Months Ended March 31,
	2015		2016
Share-based compensation	$	8.0	$	9.2
Tax benefit	3.1		3.6

There was $70.6 million and $105.0 million of unrecognized share-based compensation as of December 31, 2015 and March 31, 2016, respectively, which will be recognized over a weighted average period of approximately three years (assuming no forfeitures).

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 - December 31, 2015	1.4		$	96.18
Options granted	0.4		122.40
Options exercised	(0.1	)	80.32
Unexercised options outstanding - March 31, 2016	1.7		103.09		3.1
Exercisable at March 31, 2016	1.3		95.19		1.9

The Company granted stock options with fair values of $0.5 million and $16.0 million for the three months ended March 31, 2015 and 2016, respectively. Stock options generally vest over a period of three to four years and expire seven years after the grant date. All options have been granted with exercise prices equal to the closing price of the Company’s common stock on the grant date. In certain circumstances, option awards also require certain performance conditions to be satisfied in order for the options to be exercised.

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 three months ended March 31, 2015 and 2016 was $53.59 and $38.90 per option, respectively, based on the weighted-average grant date assumptions stated below.



	For the Three Months Ended March 31,
	2015		2016
Dividend yield	—	%	—	%
Expected volatility⁽¹⁾	27.9	%	30.6	%
Risk-free interest rate⁽²⁾	1.4	%	1.6	%
Expected life of options (in years)⁽³⁾	5.0		5.7
Forfeiture rate	—	%	—	%

___________________________


⁽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 the grant.


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

Restricted Stock

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



	Restricted Stock Units		Weighted Average Grant Date Value
Unvested units - December 31, 2015	0.6		$	192.04
Units granted	0.2		122.43
Units vested	(0.2	)	181.00
Units forfeited	(0.0)		197.79
Unvested units - March 31, 2016	0.6		169.57

The Company granted awards with fair values of $48.6 million and $27.7 million for the three months ended March 31, 2015 and 2016, respectively. These awards were valued based on the closing price of the Company’s common stock on the date of grant and contain vesting conditions requiring service over a period of four years. In certain circumstances, awards also require certain performance conditions to be satisfied and the Company may elect to settle the awards in shares of the Company’s common stock or cash.