Retirement Benefits (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021
Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Company contributions	$ 9.1	$ 21.2	$ 44.6
Defined Benefit Pension Plan | Minimum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	40.0
Defined Benefit Pension Plan | Maximum
Defined Benefit Plan Disclosure [Line Items]
Total expected contributions for current fiscal year	50.0
Other Postretirement Benefits Plan
Defined Benefit Plan Disclosure [Line Items]
Amortization of actuarial gain	$ 0.4	$ 0.4