Supplemental Financial Information - Trade Receivables, Allowances for Doubtful Accounts and Cash Discounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 94	$ 88	$ 86
Additions charged to costs and expenses	118	78	125
Deductions and other	(114)	(73)	(123)
Ending Balance	97	94	88
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	80	75	75
Additions charged to costs and expenses	18	40	31
Deductions and other	(22)	(35)	(31)
Ending Balance	76	80	75
Allowance for Cash Discounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	14	13	12
Additions charged to costs and expenses	99	39	94
Deductions and other	(92)	(38)	(92)
Ending Balance	$ 21	$ 14	$ 13