Retirement Benefits (Summary of Changes in Pension Plan Assets Fair Value Classified as Level 3) (Details) - Defined Benefit Pension Plan - Level 3 - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value at beginning of year	$ 246.6	$ 256.5
Purchases, sales, and settlements, net	80.3	(2.0)
Actual return on plan assets held at end of year	(117.9)	(7.9)
Fair Value at End of Year	209.0	246.6
Insurance Contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value at beginning of year	246.6	256.5
Purchases, sales, and settlements, net	0.0	(2.0)
Actual return on plan assets held at end of year	(91.1)	(7.9)
Fair Value at End of Year	155.5	246.6
Fixed Income Pooled Funds
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value at beginning of year	0.0	0.0
Purchases, sales, and settlements, net	80.3	0.0
Actual return on plan assets held at end of year	(26.8)	0.0
Fair Value at End of Year	$ 53.5	$ 0.0