Description of Business and Summary of Significant Accounting Policies Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jan. 31, 2017	Jan. 31, 2017	Jan. 31, 2016	Aug. 01, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit recognized	$ 7	$ 26
Net cash provided by operating activities		87	$ 129
Net cash used in financing activities		375	1,085
Cumulative effect of change in accounting principle	2	2
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash provided by operating activities			20
Net cash used in financing activities			$ (20)
Deferred income tax assets, net				$ 2
Additional Paid-in Capital | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle				6
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle	$ (4)	$ (4)
Retained Earnings | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of change in accounting principle				$ (4)