Derivative Instruments - Pre-tax Amount of Gains (Losses) on Forward Exchange Contracts Designated as Hedging Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Designated as Hedging Instrument
Unrealized Gain (Loss) On Foreign Currency Derivative Net Before Tax, Amount
Pre-tax amount of (losses) gains reclassified from accumulated other comprehensive income into the Consolidated Statement of Operations related to derivative forward exchange contracts designated as cash flow hedges	$ 17.0	$ 35.9	$ 18.0
Forward exchange contracts
Unrealized Gain (Loss) On Foreign Currency Derivative Net Before Tax, Amount
Pre-tax (losses) gains recorded in other comprehensive income related to cash flow hedges	(21.0)	17.2	70.5
Sales | Designated as Hedging Instrument
Unrealized Gain (Loss) On Foreign Currency Derivative Net Before Tax, Amount
Pre-tax amount of (losses) gains reclassified from accumulated other comprehensive income into the Consolidated Statement of Operations related to derivative forward exchange contracts designated as cash flow hedges	2.1	6.0	0.7
Cost of sales | Designated as Hedging Instrument
Unrealized Gain (Loss) On Foreign Currency Derivative Net Before Tax, Amount
Pre-tax amount of (losses) gains reclassified from accumulated other comprehensive income into the Consolidated Statement of Operations related to derivative forward exchange contracts designated as cash flow hedges	18.4	33.4	21.8
Selling, general and administrative expenses | Designated as Hedging Instrument
Unrealized Gain (Loss) On Foreign Currency Derivative Net Before Tax, Amount
Pre-tax amount of (losses) gains reclassified from accumulated other comprehensive income into the Consolidated Statement of Operations related to derivative forward exchange contracts designated as cash flow hedges	0.1	0.0	(0.9)
Interest expense | Designated as Hedging Instrument
Unrealized Gain (Loss) On Foreign Currency Derivative Net Before Tax, Amount
Pre-tax amount of (losses) gains reclassified from accumulated other comprehensive income into the Consolidated Statement of Operations related to derivative forward exchange contracts designated as cash flow hedges	$ (3.6)	$ (3.5)	$ (3.6)