Description of Business and Summary of Significant Accounting Policies Accounting Pronouncements (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Apr. 30, 2017	Apr. 30, 2017	Apr. 30, 2016	Aug. 01, 2016	Jul. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit recognized	$ 12	$ 38
Net cash provided by operating activities		1,889	$ 1,741
Net cash used in financing activities		$ (1,149)	(1,844)
Cumulative effect of change in accounting principle					$ 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			30
Net cash used in financing activities			$ (30)
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)
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)