Stock Based Compensation Plans and Other Benefit Plans (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Option Activity

Stock option transactions for the three years ended December 31, 2017 were as follows:  

						Weighted
				Weighted		Average
				Average		Remaining		Aggregate
				Exercise		Contractual		Intrinsic
	Options			Price		Term		Value
Outstanding as of December 31, 2014		17.0		$	22.75
Granted		2.2			41.91
Exercised		(1.8	)		15.56
Cancelled		(0.2	)		30.95
Outstanding as of December 31, 2015		17.2		$	25.89
Granted		2.1			46.75
Exercised		(3.0	)		16.96
Cancelled		(0.3	)		39.60
Outstanding as of December 31, 2016		16.0		$	30.06
Granted		2.1			48.39
Exercised		(1.8	)		23.06
Cancelled		(0.2	)		43.64
Outstanding as of December 31, 2017		16.1		$	33.11		5.4	$	281.6
Exercisable as of December 31, 2017		10.0		$	25.35		3.9	$	247.5

Summary of Information Relating to Options Outstanding and Exercisable

The following table summarizes information relating to options outstanding and exercisable as of December 31, 2017:

	Options Outstanding						Options Exercisable
			Weighted		Weighted				Weighted
	Outstanding		Average		Average		Exercisable		Average
Range of	as of		Remaining		Exercise		as of		Exercise
Exercise Prices	12/31/2017		ContractualLife		Price		12/31/2017		Price
$0.01 - $15.00		1.9		1.6	$	12.73		1.7	$	13.69
$15.01 - $20.00		1.0		2.4	$	16.68		1.0	$	16.68
$20.01 - $25.00		1.2		3.4	$	20.32		1.2	$	20.32
$25.01 - $30.00		1.9		4.2	$	26.92		1.9	$	26.92
$30.01 - $35.00		4.2		5.5	$	32.69		4.2	$	32.69
$35.01 - $40.00		0.0		6.7	$	35.59		0.0	$	35.59
$40.01 - $45.00		2.8		7.1	$	41.88		0.0	$	0.0
$45.01 - $50.00		1.3		8.0	$	49.20		0.0	$	0.0
$50.01 - $55.00		1.8		9.2	$	53.64		0.0	$	0.0
		16.1		5.4	$	33.11		10.0	$	25.35

Information Regarding Intrinsic Value of Stock Options Exercised and Stock Compensation Expense Related to Stock Option Awards

The following table provides information regarding the intrinsic value of stock options exercised and stock compensation expense related to stock option awards:

	2017		2016		2015
Intrinsic Value of Stock Options Exercised	$	48.0	$	91.5	$	49.0
Stock Compensation Expense Related to Stock Option Awards	$	15.7	$	14.4	$	14.8
Issued Stock Options		2.1		2.1		2.2
Weighted Average Fair Value of Stock Options issued (per share)	$	12.90	$	7.57	$	6.85
Fair Value of Stock Options Issued	$	27.8	$	16.1	$	15.3

Assumptions Used in Valuation of Issued Stock Options

The following table provides a summary of the assumptions used in the valuation of issued stock options:

	2017			2016			2015
Risk-free interest rate		2.0	%		1.7	%		2.0	%
Expected life in years		6.9			6.8			6.3
Expected volatility		16.7	%		17.0	%		17.2	%
Dividend yield		1.4	%		1.5	%		1.6	%