Derivative Instruments and Hedging Activities - Effects of Derivative Instruments on the Condensed Consolidated Statements of Income and Changes in AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Derivatives Not Designated as Hedging Instruments
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	$ 148	$ (189)	$ 241	$ (231)
Interest rate contracts | Cash Flow Hedges
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in AOCI	6	(50)	6	(42)
Interest rate contracts | Interest expense | Cash Flow Hedges
Derivative Instruments, Gain (Loss)
Loss Reclassified from AOCI into Income	(6)	(1)	(13)	(2)
Foreign currency contracts | Net Investment Hedging
Derivative Instruments, Gain (Loss)
Foreign currency contracts	7	14	(1)	10
Foreign currency contracts | Derivatives Not Designated as Hedging Instruments | Other non-operating income (expense), net
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	17	11	(3)	0
Commodity contracts | Derivatives Not Designated as Hedging Instruments | Revenues
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	(2)	6	1	8
Commodity contracts | Derivatives Not Designated as Hedging Instruments | Cost of sales
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	135	(206)	238	(239)
Commodity contracts | Derivatives Not Designated as Hedging Instruments | Operating and administrative expenses
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income	$ (2)	$ 0
Commodity contracts | Derivatives Not Designated as Hedging Instruments | Other operating income, net
Derivative Instruments, Gain (Loss)
Gain (Loss) Recognized in Income			$ 5	$ 0