Description of Business and Summary of Significant Accounting Policies (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2017 USD ($) customer $ / shares shares	Apr. 30, 2016 USD ($) customer $ / shares shares	Apr. 30, 2017 USD ($) customer $ / shares shares	Apr. 30, 2016 USD ($) customer $ / shares shares	Jul. 31, 2016 customer
Numerator:
Net income from continuing operations | $	$ 964	$ 848	$ 947	$ 846
Net income from discontinued operations | $	0	178	0	173
Net income | $	$ 964	$ 1,026	$ 947	$ 1,019
Shares used in basic per share amounts:
Weighted average common shares outstanding | shares	256	257	257	264
Shares used in diluted per share amounts:
Weighted average common shares outstanding | shares	256	257	257	264
Dilutive common equivalent shares from stock options and restricted stock awards (in shares) | shares	4	3	4	3
Dilutive weighted average common shares outstanding (in shares) | shares	260	260	261	267
Basic and diluted net income per share:
Basic net income per share from continuing operations (in USD per share)	$ 3.76	$ 3.30	$ 3.68	$ 3.21
Basic net income per share from discontinued operations (in USD per share)	0	0.70	0	0.65
Basic net income per share (in USD per share)	3.76	4.00	3.68	3.86
Diluted net income per share from continuing operations (in USD per share)	3.70	3.26	3.63	3.17
Diluted net income per share from discontinued operations (in USD per share)	0	0.68	0	0.64
Diluted net income per share (in USD per share)	$ 3.70	$ 3.94	$ 3.63	$ 3.81
Shares excluded from computation of diluted net income per share:
Weighted average stock options and restricted stock units excluded from computation due to anti-dilutive effect | shares	3	2	4	2
Customer concentration risk | Sales revenue, net
Concentration Risk [Line Items]
Concentration risk, number of customers | customer	0	0	0	0
Customer concentration risk | Accounts receivable
Concentration Risk [Line Items]
Concentration risk, number of customers | customer			0		0