Derivative Instruments and Hedging Activities - Location and Fair Values of Derivative Instruments and Hedging Activities (Detail) shares in Millions, $ in Millions	9 Months Ended
	Jun. 30, 2022 USD ($) T shares	Sep. 30, 2021 USD ($) T shares	Apr. 30, 2021 USD ($)
Derivative Instruments [Line Items]
Hedge Percentage For Foreign Exchange Transactional Exposures Minimum	70.00%
Hedge Percentage For Foreign Exchange Transactional Exposures Maximum	90.00%
Derivative assets	$ 64	$ 57
Derivative liabilities	$ 2,637	$ 2,936
Interest Rate Swaps
Derivative Instruments [Line Items]
Derivative, Notional Amount			$ 500
Copper [Member]
Derivative Instruments [Line Items]
Derivative, Nonmonetary Notional Amount | T	3,382	2,656
Aluminum [Member]
Derivative Instruments [Line Items]
Derivative, Nonmonetary Notional Amount | T	6,942	5,159
Equity swap
Derivative Instruments [Line Items]
Derivative, amount of hedged ordinary shares | shares	0.0	0.3
Derivative, Amount of Hedged Item		$ 23
Designated as Hedging Instrument
Derivative Instruments [Line Items]
Derivative assets	$ 22	17
Derivative liabilities	2,624	2,930
Designated as Hedging Instrument | Other Current Assets | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative assets	22	15
Designated as Hedging Instrument | Other Current Assets | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative assets	0	2
Designated as Hedging Instrument | Other Noncurrent Assets | Equity swap
Derivative Instruments [Line Items]
Derivative assets	0	0
Designated as Hedging Instrument | Other Current Liabilities | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	11	11
Designated as Hedging Instrument | Other Current Liabilities | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	10	1
Designated as Hedging Instrument | Long-term Debt | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Derivative liabilities	2,603	2,918
Not Designated as Hedging Instrument
Derivative Instruments [Line Items]
Derivative assets	42	40
Derivative liabilities	13	6
Not Designated as Hedging Instrument | Other Current Assets | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative assets	42	17
Not Designated as Hedging Instrument | Other Current Assets | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative assets	0	0
Not Designated as Hedging Instrument | Other Noncurrent Assets | Equity swap
Derivative Instruments [Line Items]
Derivative assets	0	23
Not Designated as Hedging Instrument | Other Current Liabilities | Foreign Currency Exchange Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	13	6
Not Designated as Hedging Instrument | Other Current Liabilities | Commodity Derivatives
Derivative Instruments [Line Items]
Derivative liabilities	0	0
Not Designated as Hedging Instrument | Long-term Debt | Foreign Currency Denominated Debt [Member]
Derivative Instruments [Line Items]
Derivative liabilities	$ 0	0
Two Point Zero Percent Due Two Thousand Thirty One | Johnson Controls International plc (JCI) and Tyco Fire & Security Finance S.C.A. (TFSCA)
Derivative Instruments [Line Items]
Debt Instrument, Face Amount		$ 500