Derivative Instruments and Hedging Activities - Location and Amount of Gains and Losses on Derivative Instruments and Related Hedge Items (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gain (Loss) Recognized in Income, Derivative not Recognized as Hedge	$ 123	$ (26)	$ 166	$ 29
Foreign Currency Exchange Derivatives \| Cost of Sales
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gain (Loss) Recognized in Income, Derivative not Recognized as Hedge	2	4	(4)	4
Foreign Currency Exchange Derivatives \| Selling, General And Administrative
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gain (Loss) Recognized in Income, Derivative not Recognized as Hedge	3	0	1	0
Foreign Currency Exchange Derivatives \| Net Financing Charges
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gain (Loss) Recognized in Income, Derivative not Recognized as Hedge	100	(10)	145	49
Equity swap \| Selling, General And Administrative
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gain (Loss) Recognized in Income, Derivative not Recognized as Hedge	18	(20)	24	(24)
Cash Flow Hedging
Cash Flow Hedges Derivative Instruments at Fair Value, Net [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	10	(11)	14	(1)
Amount of Gain (Loss) Reclassified from AOCI into Income	(1)	2	0	2
Cash Flow Hedging \| Foreign Currency Exchange Derivatives
Cash Flow Hedges Derivative Instruments at Fair Value, Net [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	10	(7)	13	2
Cash Flow Hedging \| Foreign Currency Exchange Derivatives \| Cost of Sales
Cash Flow Hedges Derivative Instruments at Fair Value, Net [Abstract]
Amount of Gain (Loss) Reclassified from AOCI into Income	1	2	3	3
Cash Flow Hedging \| Commodity Derivatives
Cash Flow Hedges Derivative Instruments at Fair Value, Net [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0	(4)	1	(3)
Cash Flow Hedging \| Commodity Derivatives \| Cost of Sales
Cash Flow Hedges Derivative Instruments at Fair Value, Net [Abstract]
Amount of Gain (Loss) Reclassified from AOCI into Income	(2)	0	(3)	(1)
Net Investment Hedging [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Gains (losses) reclassified from CTA to income for the Company's outstanding net investment hedges			0	0
Pre-tax losses on net investment hedges recorded in CTA within other comprehensive income (loss)	$ 144	$ 46	$ 9	$ (12)

Cash Flow Hedge [Abstract]

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Gains (losses) reclassified from CTA to income for the Company's outstanding net investment hedges

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Amount of realized and unrealized gain (loss) of derivative instruments not designated or qualifying as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
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The amount of net gains or losses on foreign currency cash flow hedges reclassified during the period to earnings from accumulated other comprehensive income upon the hedged transaction affecting earnings.

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Amount, before tax and reclassification, of gain (loss) from derivative designated and qualifying as net investment hedge.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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