Supplemental Information (Shareholder Activism Costs) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Shareholder Activism Costs [Line Items]
Legal, executive separation, and other professional service fees in connection with response to proxy contest	$ 25.0	$ 0.0	$ 86.3	$ 0.0
Legal, executive separation, and other professional service fees in connection with response to proxy contest, after tax	18.8		71.7
Amount of related party transaction (sales to and other income)	(90.0)	(240.0)	(80.0)	(255.0)
Severance and other cash benefits	24.1	$ 0.0	2,952.0	$ 57.0
Mantle Ridge LP and Affiliates Transaction | Affiliated Entity
Shareholder Activism Costs [Line Items]
Amount of related party transaction (sales to and other income)	24.7
Executive Separation Costs
Shareholder Activism Costs [Line Items]
Share-based payment arrangement, accelerated cost			$ 22.4
Severance and other cash benefits	$ 7.3