Supplemental Financial Information - Trade Receivables, Allowances for Doubtful Accounts and Cash Discounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	$ 42	$ 50	$ 45
Additions charged to costs and expenses	80	46	49
Deductions and other	(61)	(54)	(44)
Ending Balance	62	42	50
Allowance for Doubtful Accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	30	41	36
Additions charged to costs and expenses	33	6	9
Deductions and other	(11)	(16)	(3)
Ending Balance	53	30	41
Allowance for Cash Discounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning Balance	12	9	9
Additions charged to costs and expenses	47	41	40
Deductions and other	(50)	(38)	(41)
Ending Balance	$ 9	$ 12	$ 9