Derivative Instruments and Hedging Activities - Effects of Derivative Instruments on Condensed Consolidated Statements of Income and Changes in AOCI and Noncontrolling Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Derivatives Not Designated as Hedging Instruments:
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	$ 1,542	$ (42)	$ (299)
Derivatives Not Designated as Hedging Instruments: | Foreign currency contracts | Other non-operating income (expense), net
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	9	(20)	38
Derivatives Not Designated as Hedging Instruments: | Commodity contracts | Revenues
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	(17)	10	7
Derivatives Not Designated as Hedging Instruments: | Commodity contracts | Cost of sales
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	1,545	(32)	(344)
Derivatives Not Designated as Hedging Instruments: | Commodity contracts | Other operating income, net
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	5	0	0
Cash Flow Hedges:
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	4	(53)	(10)
Gain (Loss) Reclassified from AOCI into Income	(25)	(13)	(4)
Cash Flow Hedges: | Foreign currency contracts
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	0	0	1
Cash Flow Hedges: | Foreign currency contracts | Cost of sales
Derivative Instruments, Gain (Loss)
Gain (Loss) Reclassified from AOCI into Income	0	0	2
Cash Flow Hedges: | Interest rate contracts
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	4	(53)	(11)
Cash Flow Hedges: | Interest rate contracts | Interest expense
Derivative Instruments, Gain (Loss)
Gain (Loss) Reclassified from AOCI into Income	(25)	(13)	(6)
Net Investment Hedges: | Foreign currency contracts
Derivative Instruments, Gain (Loss)
Foreign currency contracts	$ 4	$ (1)	$ 17