Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2013

Stock based compensation expense for the years ended December 31, 2013, 2012 and 2011 was as follows (in millions):

	2013		2012		2011
Stock based compensation	$	53.4	$	40.8	$	31.7
Tax benefit recognized in net income		18.7		14.3		11.1
Windfall tax benefit, net		16.0		30.8		12.7

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The Company estimates the fair value of its option awards using the Black-Scholes option valuation model that uses the assumptions noted in the following table. The stock volatility for each grant is measured using the weighted-average of historical daily price changes of the Company's common stock over the most recent period equal to the expected life of the grant. The expected term of options granted is derived from historical data to estimate option exercises and employee terminations, and represents the period of time that options granted are expected to be outstanding. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant. The weighted-average fair value of options granted in 2013, 2012 and 2011 were calculated using the following weighted-average assumptions:

	2013		2012		2011
Weighted-average fair value ($)		37.08		30.25		24.45
Risk-free interest rate (%)		0.86		0.77		1.91
Average expected option life (years)		5.19		5.24		5.34
Expected volatility (%)		36.09		36.51		35.27
Expected dividend yield (%)		0.56		0.58		0.60

Schedule of Share-based Compensation, Stock Option Activity

The following table summarizes the Company's activities with respect to its stock option plans for the years ended December 31, 2013 and 2012:

	Number of shares	Weighted-average exercise price per share	Weighted-average contractual term	Aggregate intrinsic value
Outstanding at January 1, 2012	3,822,662	$ 50.44
Granted	538,100	95.27
Exercised	(1,389,069)	40.46
Canceled	(53,498)	70.01
Outstanding at December 31, 2012	2,918,195	63.15	6.52	$ 141,029,378
Granted	601,350	117.78
Exercised	(424,945)	56.48
Canceled	(106,164)	98.74
Outstanding at December 31, 2013	2,988,436	74.00	6.22	$ 193,279,214
Exercisable at December 31, 2013	1,859,725	$ 56.99	4.84	$ 151,929,651

Summary of Options Outstanding and Exercisable, by Range of Exercise Prices

The following table summarizes information for stock options outstanding at December 31, 2013:

	Outstanding options			Exercisable options
Exercise price	Number	Average exercise price	Average remaining life (years)	Number	Average exercise price
$ 14.09 - 28.17	157,638	$ 23.70	0.2	157,638	$ 23.70
28.17 - 42.26	126,574	41.81	5.2	126.574	41.81
42.27 - 56.34	1,113,058	53.79	4.4	1,113,058	53.79
56.35 - 70.43	96,800	67.88	7.5	45,300	66.71
70.44 - 84.52	453,392	74.63	7.1	278,034	75.21
84.53 - 98.60	419,924	94.00	8.1	130,085	93.91
98.61 - 112.69	48,700	103.41	8.6	9,036	103.64
112.70 - 126.77	547,350	117.03	9.2	-	-
126.78 - 140.86	25,000	131.54	9.6	-	-
$ 14.09 - 140.86	2,988,436	$ 74.00	6.2	1,859,725	$ 56.99

Schedule of Nonvested Restricted Stock Awards Activity

Restricted Stock Grants - During 2013 and 2012, the Company granted 399,540 and 374,307 shares, respectively, of restricted stock to certain employee and director participants under the 2006 Plan. Restricted stock grants generally vest over a period of 1 to 3 years. The Company recorded $36.5 million, $25.9 million and $19.5 million of compensation expense related to outstanding shares of restricted stock held by employees and directors during 2013, 2012 and 2011, respectively. A summary of the Company's nonvested shares activity for 2013 and 2012 is as follows:

	Number of shares			Weighted-average fair value
Nonvested at December 31, 2011		753,811		$	61.15
Granted		374,307			95.78
Vested		(551,051	)		64.59
Forfeited		(5,162	)		70.56
Nonvested at December 31, 2012		571,905		$	80.96
Granted		399,540			117.74
Vested		(373,946	)		126.80
Forfeited		(23,649	)		124.48
Nonvested at December 31, 2013		573,850		$	103.44