Business Segment Information (Reconciliation of Operating Income) (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting Information [Line Items]
Operating income (loss)	$ 643.6	$ 666.9
Shareholder activism costs	(29.9)	0.0
Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	$ 673.5	$ 666.9