Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Reclassification of terminated interest rate swaps to interest expense within the next 12 months	$ 6,000,000
Cash flow hedges	(67,000,000)	$ (6,000,000)	$ 1,000,000
Debt | Net Investment Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	1,500,000,000	1,400,000,000
Forward exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	2,500,000,000	2,300,000,000
Currency Swap
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	3,000,000,000.0	2,300,000,000
Fixed To Floating
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	375,000,000	375,000,000
Interest rate swaps | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	1,500,000,000	$ 1,500,000,000
Cash flow hedges	75,000,000
Commodity forward contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Derivative, Notional Amount	$ 0