Derivative and Hedging Instruments - Schedule of Derivative Instruments at Gross Value (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Derivative [Line Items]
Assets	$ 62	$ 103
Liabilities	319	226
Senior Notes
Derivative [Line Items]
Hedged liability, fair value hedge	$ 2,400	$ 3,900
Hedged Liability, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt
Foreign exchange forward contracts | Designated as Hedging Instruments: | Prepaid expenses and other current assets
Derivative [Line Items]
Assets	$ 45	$ 49
Foreign exchange forward contracts | Designated as Hedging Instruments: | Accrued liabilities
Derivative [Line Items]
Liabilities	196	74
Foreign exchange forward contracts | Not Designated as Hedging Instruments: | Prepaid expenses and other current assets
Derivative [Line Items]
Assets	17	18
Foreign exchange forward contracts | Not Designated as Hedging Instruments: | Accrued liabilities
Derivative [Line Items]
Liabilities	15	17
Cross-currency swaps | Designated as Hedging Instruments: | Other assets
Derivative [Line Items]
Assets	0	36
Cross-currency swaps | Designated as Hedging Instruments: | Accrued liabilities and other liabilities
Derivative [Line Items]
Liabilities	58	2
Interest rate swaps | Designated as Hedging Instruments: | Accrued liabilities and other liabilities
Derivative [Line Items]
Liabilities	$ 50	$ 133