Retirement Benefits - Defined Benefit Plan Change in Fair Value of Plan Assets Level Three (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	$ 4,192.2
Plan assets at end of year	2,903.9	$ 4,192.2
Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	111.8	115.7
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	(51.6)	(5.6)
Purchases, Sales, Issuances, and Settlements, Net	(1.5)	1.7
Plan assets at end of year	58.7	111.8
U.S. Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	3,047.3
Plan assets at end of year	2,091.3	3,047.3
U.S. Plans | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	0.9
Plan assets at end of year	0.0	0.9
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	0.9	0.9
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	0.0	0.0
Purchases, Sales, Issuances, and Settlements, Net	(0.9)	0.0
Plan assets at end of year	0.0	0.9
Non-U.S. Plans
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	1,144.9
Plan assets at end of year	812.6	1,144.9
Non-U.S. Plans | Level 3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Plan assets at beginning of year	110.9
Plan assets at end of year	58.7	110.9
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	106.2	110.2
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	(50.9)	(5.7)
Purchases, Sales, Issuances, and Settlements, Net	(0.4)	1.7
Plan assets at end of year	54.9	106.2
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	4.7	4.6
Realized Gains (Losses)	0.0	0.0
Unrealized Gains (Losses)	(0.7)	0.1
Purchases, Sales, Issuances, and Settlements, Net	(0.2)	0.0
Plan assets at end of year	$ 3.8	$ 4.7