Derivative Instruments - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
Sep. 30, 2026	Sep. 30, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Maximum length of time hedged in cash flow hedge	2 years
Net unrealized losses on cash flow hedges to be reclassified into earnings during the next 12 months	$ 3
Accumulated other comprehensive loss	(478)	$ (657)
Forward exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
U.S. dollar-equivalent gross notional amount	1,392
Forward exchange contracts \| Not Designated as Hedging Instrument
Derivative Instruments, Gain (Loss) [Line Items]
U.S. dollar-equivalent gross notional amount	531
Net investment hedges
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated other comprehensive loss	47	17
Cash Flow Hedging \| Forward exchange contracts
Derivative Instruments, Gain (Loss) [Line Items]
U.S. dollar-equivalent gross notional amount	861
Cash Flow Hedging \| Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
U.S. dollar-equivalent gross notional amount	$ 850	$ 800

Amount, after tax, of accumulated increase (decrease) in equity from transaction and other event and circumstance from nonowner source.

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