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, 2020	Sep. 30, 2019	Sep. 30, 2018
Derivatives Not Designated as Hedging Instruments:
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	$ (42)	$ (299)	$ 166
Derivatives Not Designated as Hedging Instruments: | Foreign currency contracts | Other non-operating (expense) income, net
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	(20)	38	16
Derivatives Not Designated as Hedging Instruments: | Commodity contracts | Cost of sales
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	(32)	(344)	155
Derivatives Not Designated as Hedging Instruments: | Commodity contracts | Revenues
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	10	7	(5)
Cash Flow Hedges:
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	(53)
Gain (Loss) Recognized in AOCI		(10)	2
Gain (Loss) Reclassified from AOCI into Income	(13)
Gain (Loss) Reclassified from AOCI into Income		(4)	(7)
Cash Flow Hedges: | Foreign currency contracts
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	0
Gain (Loss) Recognized in AOCI		1	0
Cash Flow Hedges: | Foreign currency contracts | Cost of sales
Derivative Instruments, Gain (Loss)
Gain (Loss) Reclassified from AOCI into Income	0
Gain (Loss) Reclassified from AOCI into Income		2	(3)
Cash Flow Hedges: | Cross-currency swaps
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	0
Gain (Loss) Recognized in AOCI		0	2
Cash Flow Hedges: | Cross-currency swaps | Interest expense /other operating income, net
Derivative Instruments, Gain (Loss)
Gain (Loss) Reclassified from AOCI into Income	0
Gain (Loss) Reclassified from AOCI into Income		0	1
Cash Flow Hedges: | Interest rate contracts
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	(53)
Gain (Loss) Recognized in AOCI		(11)	0
Cash Flow Hedges: | Interest rate contracts | Interest expense
Derivative Instruments, Gain (Loss)
Gain (Loss) Reclassified from AOCI into Income	(13)
Gain (Loss) Reclassified from AOCI into Income		(6)	(5)
Net Investment Hedges: | Foreign currency contracts
Derivative Instruments, Gain (Loss)
Foreign currency contracts	$ (1)
Foreign currency contracts		$ 17	$ 0