STOCK-BASED COMPENSATION

3 Months Ended

Mar. 31, 2016

NOTE 2. STOCK-BASED COMPENSATION

Presented below is a summary of the stock-based compensation cost and associated tax benefit included in the accompanying consolidated statements of operations:

	Three Months Ended
	March 31,
	2016		2015
Stock-based compensation cost	$	25.4	$	22.7
Tax benefit	$	8.4	$	7.9

During the first three months of 2016, the Company granted 0.5 million employee stock options, which had a weighted average grant date fair value of $22.93 per share based on the Black-Scholes option-pricing model. The Company also granted 1.2 million shares of restricted stock in the first three months of 2016, which had a weighted average grant date fair value of $80.83 per share. Both the employee stock options and restricted stock generally vest ratably over a four-year period. Additionally, the Company granted approximately 0.2 million shares of performance-based awards whereby the number of shares that ultimately vest are based on the achievement of certain non-market based performance metrics of the Company over a three-year period. The weighted average grant date fair value of these awards was $76.45 per share.

The following weighted average assumptions were used in determining the fair value for options granted in 2016:

Expected dividend yield	1.83%
Expected stock volatility	32.3%
Risk-free interest rate	1.60%
Expected holding period	6.8 years
Grant date fair value	$22.93

Unrecognized compensation expense at March 31, 2016 was $16.0 million and $172.5 million for stock options and unvested restricted stock, respectively, which is expected to be recognized over a weighted average period of 1.5 years and 1.9 years, respectively. Additionally, there was $23.8 million of unrecognized compensation expense relating to the aforementioned non-market based performance-based awards, which is expected to be recognized over a weighted average period of 1.2 years.

The following tables summarize information relating to stock option exercises and restricted stock vesting:

	Three Months Ended
	March 31,
Exercise of stock options:	2016		2015
Proceeds from stock option exercises	$	22.8	$	33.5
Aggregate intrinsic value	$	11.0	$	32.1
Tax benefit realized upon exercise	$	3.9	$	11.9
Number of shares exercised		0.4		0.7

	Three Months Ended
	March 31,
Vesting of restricted stock:	2016		2015
Fair value of shares vested	$	89.3	$	108.9
Tax benefit realized upon vesting	$	29.5	$	35.9
Number of shares vested		1.0		1.1

	Three Months Ended
	March 31,
Vesting of performance-based restricted stock:	2016		2015
Fair value of shares vested	$	23.6	$	43.1
Tax benefit realized upon vesting	$	8.4	$	16.1
Number of shares vested		0.2		0.5