Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	$ 46	$ 51	$ 45
Additions Charged to Expense/ Revenue	58	44	49
Deductions	(99)	(49)	(43)
Valuation and qualifying accounts, ending balance	5	46	51
Reserve for product returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	7	7	12
Additions Charged to Expense/ Revenue	93	76	70
Deductions	(90)	(76)	(75)
Valuation and qualifying accounts, ending balance	10	7	7
Reserve for promotional discounts and rebates
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	19	14	12
Additions Charged to Expense/ Revenue	99	113	103
Deductions	(108)	(108)	(101)
Valuation and qualifying accounts, ending balance	$ 10	$ 19	$ 14