Share-Based Compensation (Compensation Cost Recognized in Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Before-tax share-based compensation cost	$ 11.0	$ 17.6	$ 65.8	$ 46.0
Income tax benefit	(2.8)	(4.2)	(15.8)	(11.1)
After-tax share-based compensation cost	$ 8.2	$ 13.4	50.0	$ 34.9
Executive Separation Costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, accelerated cost			$ 22.4