Income Taxes - Components of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Jul. 31, 2017	Jul. 31, 2016
Deferred tax assets:
Accruals and reserves not currently deductible	$ 35	$ 33
Deferred revenue	74	56
Deferred rent	13	14
Accrued and deferred compensation	62	55
Loss and tax credit carryforwards	71	51
Stock-based compensation	70	62
Other, net	14	11
Total gross deferred tax assets	339	282
Valuation allowance	(64)	(40)
Total deferred tax assets	275	242
Deferred tax liabilities:
Intangible assets	93	86
Property and equipment	57	24
Total deferred tax liabilities	150	110
Net deferred tax assets	125	132
Deferred Tax Assets, Net [Abstract]
Long-term deferred income taxes	132	139
Long-term deferred income taxes included in other long-term obligations	$ (7)	$ (7)