Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2023
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Company contributions			$ 25.6	$ 22.0	$ 32.6
Defined Benefit Pension Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	$ 35.0		35.0
Defined Benefit Pension Plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	45.0		45.0
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Amortization of actuarial gain	$ 0.1	$ 0.5	$ 0.4	$ 1.5