Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (Loss) on Derivative Used in Net Investment Hedge, after Tax	$ 81,000,000	$ (159,000,000)
Reclassification of terminated interest rate swaps to interest expense within the next 12 months	6,000,000
Forward exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	3,100,000,000	2,500,000,000
Fixed To Floating
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	1,200,000,000	375,000,000
Commodity forward contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	0	$ 0
Euro Member Countries, Euro | Debt [Member] | Net Investment Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	2,700,000,000
United Kingdom, Pounds | Debt [Member] | Net Investment Hedging [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Notional amount	$ 324,000,000