Valuation and Qualifying Accounts [Schedule II] (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2015	Jul. 31, 2014	Jul. 31, 2013
Allowance for doubtful accounts
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves, beginning balance	$ 40	$ 38	$ 46
Valuation allowances and reserves, additions charged to expense/revenue	57	50	49
Valuation allowances and reserves, deductions	(52)	(48)	(57)
Valuation allowances and reserves, ending balance	45	40	38
Reserve for product returns
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves, beginning balance	15	14	16
Valuation allowances and reserves, additions charged to expense/revenue	68	74	92
Valuation allowances and reserves, deductions	(71)	(73)	(94)
Valuation allowances and reserves, ending balance	12	15	14
Reserve for rebates
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation allowances and reserves, beginning balance	21	14	16
Valuation allowances and reserves, additions charged to expense/revenue	97	103	107
Valuation allowances and reserves, deductions	(106)	(96)	(109)
Valuation allowances and reserves, ending balance	$ 12	$ 21	$ 14