Supplemental Financial Information - Trade Receivables, Allowances for Doubtful Accounts and Cash Discounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 62	$ 42	$ 50
Additions charged to costs and expenses	60	80	46
Deductions and other	(55)	(61)	(54)
Ending Balance	67	62	42
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	53	30	41
Additions charged to costs and expenses	23	33	6
Deductions and other	(14)	(11)	(16)
Ending Balance	61	53	30
Allowance for Cash Discounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	9	12	9
Additions charged to costs and expenses	37	47	41
Deductions and other	(40)	(50)	(38)
Ending Balance	$ 6	$ 9	$ 12