Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Jul. 31, 2017
Income Tax Disclosure [Abstract]
Excess tax benefits for provision for income taxes	$ 25	$ 19
Effective tax rate	72.00%	58.00%
Effective income tax rate reconciliation, excluding discrete tax benefits, percent	33.00%	34.00%
Federal statutory income tax rate	35.00%	35.00%
Total amount of unrecognized tax benefits			$ 61
Unrecognized tax benefits, net of related deferred tax assets			38
Favorable net impact to income tax expense due to recognition of tax benefits			$ 38