Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2020	Jul. 31, 2019	Jul. 31, 2018
Allowance for doubtful accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	$ 3	$ 5	$ 46
Additions Charged to Expense/ Revenue	68	59	58
Deductions	(59)	(61)	(99)
Valuation and qualifying accounts, ending balance	12	3	5
Reserve for returns and credits
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	24	17	14
Additions Charged to Expense/ Revenue	170	190	167
Deductions	(170)	(183)	(164)
Valuation and qualifying accounts, ending balance	24	24	17
Reserve for promotional discounts and rebates
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation and qualifying accounts, beginning balance	11	10	19
Additions Charged to Expense/ Revenue	73	92	99
Deductions	(73)	(91)	(108)
Valuation and qualifying accounts, ending balance	$ 11	$ 11	$ 10