Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross unrecognized tax benefits, beginning balance	$ 61	$ 60	$ 56
Increases related to tax positions from prior fiscal years, including acquisitions	10	8	7
Decreases related to tax positions from prior fiscal years	(3)	(8)	(7)
Increases related to tax positions taken during current fiscal year	23	9	15
Settlements with tax authorities	(1)	(8)	(11)
Gross unrecognized tax benefits, ending balance	90	61	60
Unrecognized tax benefits net of related deferred tax assets	57
Favorable net impact to income tax expense due to recognition of tax benefits	57
Interest and penalties related to unrecognized tax benefits	0	0
Interest and penalties that we recognized	$ 0	$ 0	$ 0