Share-Based Compensation (Total Before-Tax Share-Based Compensation Cost by Type of Program) (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Before-Tax Share-Based Compensation	$ 41.2	$ 38.8	$ 40.7
Deferred Stock Units
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Before-Tax Share-Based Compensation	41.1	38.3	34.5
Stock Options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Before-Tax Share-Based Compensation	0.0	0.2	1.4
Restricted Stock
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Before-Tax Share-Based Compensation	$ 0.1	$ 0.3	$ 4.8