Share-Based Compensation (Compensation Cost Recognized in Income Statement) (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 6 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2015
Mar. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]        
Before-Tax Share-Based Compensation $ 12.9 $ 11.6 $ 24.8 $ 23.4
Income Tax Benefit (4.7) (3.9) (8.7) (8.2)
After-Tax Share-Based Compensation $ 8.2 $ 7.7 $ 16.1 $ 15.2