Share-Based Compensation (Compensation Cost Recognized in Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Sep. 30, 2025
Share-Based Payment Arrangement [Abstract]
Before-tax share-based compensation cost	$ 12.3	$ 11.0	$ 38.6	$ 65.8
Income tax benefit	(2.9)	(2.8)	(9.1)	(15.8)
After-tax share-based compensation cost	$ 9.4	$ 8.2	$ 29.5	$ 50.0
Executive Separation Costs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment arrangement, accelerated cost					$ 22.4