Derivative Instruments and Hedging Activities - Schedule of Effects of Derivative Instruments on Condensed Consolidated Statements of Income and Changes in AOCI and Noncontrolling Interest (Details) - Derivatives Not Designated as Hedging Instruments: - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	$ (3)	$ (107)	$ (1,781)
Interest rate contracts | Cash Flow Hedges:
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	14	(19)	25
Interest rate contracts | Cash Flow Hedges: | Interest expense
Derivative Instruments, Gain (Loss)
Gain (Loss) Reclassified from AOCI into Income	3	49	40
Commodity contracts | Revenues
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	(1)	1	11
Commodity contracts | Cost of sales
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	3	(92)	(1,771)
Commodity contracts | Other operating expense (income), net
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	(1)	3	2
Foreign currency contracts | Other non-operating income (expense), net
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	(4)	(19)	(23)
Foreign currency contracts | Net Investment Hedges:
Derivative Instruments, Gain (Loss)
Foreign currency contracts	$ (9)	$ (5)	$ (21)