Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Sep. 30, 2022
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Company contributions				$ 15.4	$ 16.1	$ 44.7
Curtailment gain				1.9	0.0
Defined Benefit Pension Plan | International
Defined Benefit Plan Disclosure [Line Items]
Curtailment gain		$ 1.9		1.9	0.0
Decrease in projected benefit obligation		9.1
Decrease in accumulated other comprehensive loss		$ 9.1
Defined Benefit Pension Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	$ 25.0			25.0
Defined Benefit Pension Plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	35.0			35.0
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Amortization of actuarial gain	$ 0.4		$ 0.4	$ 1.0	$ 0.8