Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Allowance for doubtful accounts
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation and qualifying accounts, beginning balance	$ 51	$ 45	$ 40
Additions Charged to Expense/ Revenue	44	49	57
Deductions	(49)	(43)	(52)
Valuation and qualifying accounts, ending balance	46	51	45
Reserve for product returns
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation and qualifying accounts, beginning balance	7	12	15
Additions Charged to Expense/ Revenue	76	70	79
Deductions	(76)	(75)	(82)
Valuation and qualifying accounts, ending balance	7	7	12
Reserve for promotional discounts and rebates
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation and qualifying accounts, beginning balance	14	12	21
Additions Charged to Expense/ Revenue	113	103	97
Deductions	(108)	(101)	(106)
Valuation and qualifying accounts, ending balance	$ 19	$ 14	$ 12