Description of Business and Summary of Significant Accounting Policies - Schedule of shares used in the computation of basic and diluted net income per share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Jul. 31, 2018	Apr. 30, 2018	Jan. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2018	Jul. 31, 2017	Jul. 31, 2016
Numerator:
Net income									$ 1,211	$ 971	$ 806
Net income from discontinued operations									0	0	173
Net income	$ 49	$ 1,200	$ (21)	$ (17)	$ 24	$ 964	$ 13	$ (30)	$ 1,211	$ 971	$ 979
Shares used in basic per share amounts:
Weighted average common shares outstanding (in shares)									256	257	262
Shares used in diluted per share amounts:
Weighted average common shares outstanding (in shares)									256	257	262
Dilutive common equivalent shares from stock options and restricted stock awards (in shares)									5	4	3
Dilutive weighted average common shares outstanding (in shares)									261	261	265
Basic and diluted net income per share:
Basic net income per share from continuing operations (in dollars per share)									$ 4.72	$ 3.78	$ 3.08
Basic net income per share from discontinued operations (in dollars per share)									0	0	0.65
Basic net income per share (in dollars per share)	$ 0.19	$ 4.68	$ (0.08)	$ (0.07)	$ 0.09	$ 3.76	$ 0.05	$ (0.12)	4.72	3.78	3.73
Diluted net income per share from continuing operations (in dollars per share)									4.64	3.72	3.04
Diluted net income per share from discontinued operations (in dollars per share)									0	0	0.65
Diluted net income per share (in dollars per share)	$ 0.18	$ 4.59	$ (0.08)	$ (0.07)	$ 0.09	$ 3.70	$ 0.05	$ (0.12)	$ 4.64	$ 3.72	$ 3.69
Weighted average stock options and restricted stock units that have been excluded from dilutive common equivalent shares outstanding due to their anti-dilutive effect (in shares)									0	3	2