Stock Based Compensation Plans

3 Months Ended

Mar. 31, 2019

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock Based Compensation Plans

6. Stock Based Compensation Plans

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, 2018		14.7		$	37.63
Exercised		(0.7	)		28.49
Outstanding at March 31, 2019		14.0		$	38.00		5.4	$	465.4
Exercisable at March 31, 2019		8.9		$	30.90		4.1	$	357.6

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,
	2019		2018
Intrinsic Value of Stock Options Exercised	$	24.1	$	30.0
Stock Compensation Expense Related to Stock Option Awards	$	2.3	$	2.7