Retirement Benefits - Defined Benefit Plan Change in Fair Value of Plan Assets Level Three (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	$ 2,457.4
Plan assets at end of year	2,779.2	$ 2,457.4
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	67.6	58.7
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	8.4	9.6
Purchases, Sales, Issuances, and Settlements, Net	(2.1)	(0.7)
Plan assets at end of year	73.9	67.6
U.S. Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	1,618.8
Plan assets at end of year	1,800.4	1,618.8
U.S. Plans | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	0.0
Plan assets at end of year	0.0	0.0
Non-U.S. Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	838.6
Plan assets at end of year	978.8	838.6
Non-U.S. Plans | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	67.6
Plan assets at end of year	73.9	67.6
Non-U.S. Plans | Level 3 | Insurance contracts
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	65.2	54.9
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	8.4	9.6
Purchases, Sales, Issuances, and Settlements, Net	(1.8)	0.7
Plan assets at end of year	71.8	65.2
Non-U.S. Plans | Level 3 | Other
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	2.4	3.8
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	0.0	0.0
Purchases, Sales, Issuances, and Settlements, Net	(0.3)	(1.4)
Plan assets at end of year	$ 2.1	$ 2.4