Income Taxes - Components of deferred tax assets and liabilities (Details) - USD ($) $ in Millions	Jul. 31, 2018	Jul. 31, 2017
Deferred tax assets:
Accruals and reserves not currently deductible	$ 12	$ 35
Deferred revenue	46	74
Deferred rent	8	13
Accrued and deferred compensation	41	62
Loss and tax credit carryforwards	97	71
Share-based compensation	49	70
Other, net	4	14
Total gross deferred tax assets	257	339
Valuation allowance	(93)	(64)
Total deferred tax assets	164	275
Deferred tax liabilities:
Intangible assets	65	93
Property and equipment	19	57
Total deferred tax liabilities	84	150
Net deferred tax assets	80	125
Deferred Tax Assets, Net [Abstract]
Long-term deferred income taxes	87	132
Long-term deferred income taxes included in other long-term obligations	$ (7)	$ (7)