Share-Based Compensation Plans (Compensation Expense for Share-Based Arrangements and Tax Impacts) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 21.6	$ 20.4	$ 106.2	$ 66.2
Tax Benefits Recognized	8.5	7.7	40.4	25.0
Restricted Stock Unit Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	15.8	15.0	72.6	45.0
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	0.9	0.9	8.2	8.1
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense	$ 4.9	$ 4.5	$ 25.4	$ 13.1