Stock Based Compensation Plans (Tables)

3 Months Ended

Mar. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Option Activity

The following table provides a summary of option activity:

						Weighted
				Weighted		Average
				Average		Remaining		Aggregate
				Exercise		Contractual		Intrinsic
	Options			Price		Term		Value
Outstanding at December 31, 2017		16.1		$	33.11
Exercised		(0.9	)		17.73
Cancelled		(0.1	)		48.20
Outstanding at March 31, 2018		15.1		$	33.99		5.4	$	253.8
Exercisable at March 31, 2018		9.0		$	26.13		3.9	$	219.1

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:  

	Three Months Ended
	March 31,		March 31,
	2018		2017
Intrinsic Value of Stock Options Exercised	$	30.0	$	27.2
Stock Compensation Expense Related to Stock Option Awards	$	2.7	$	1.7