Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2017
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	$ 5	$ 46	$ 51
Additions Charged to Expense/ Revenue	59	58	44
Deductions	(61)	(99)	(49)
Valuation and qualifying accounts, ending balance	3	5	46
Reserve for returns and credits
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	17	14	14
Additions Charged to Expense/ Revenue	190	167	160
Deductions	(183)	(164)	(160)
Valuation and qualifying accounts, ending balance	24	17	14
Reserve for promotional discounts and rebates
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	10	19	14
Additions Charged to Expense/ Revenue	92	99	113
Deductions	(91)	(108)	(108)
Valuation and qualifying accounts, ending balance	$ 11	$ 10	$ 19