Stockholders' Equity - Stock Option Activity and Related Share-Based Compensation Expense (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015	Jul. 31, 2017
Summary of stock option activity, number of shares
Number of shares, Beginning Balance (in shares)	8,346	8,713	10,938
Granted (in shares)	1,786	2,553	1,981
Exercised (in shares)	(2,213)	(2,566)	(3,704)
Canceled or expired (in shares)	(431)	(354)	(502)
Number of shares, Ending Balance (in shares)	7,488	8,346	8,713
Weighted Average Exercise Price Per Share
Weighted average exercise price per share, Beginning Balance (in dollars per share)	$ 88.55	$ 69.13	$ 52.67
Granted (in dollars per share)	135.24	113.08	106.86
Exercised (in dollars per share)	69.12	48.93	41.65
Canceled or expired (in dollars per share)	104.78	74.56	62.32
Weighted average exercise price per share, Ending Balance (in dollars per share)	$ 104.50	$ 88.55	$ 69.13
Stock Options Outstanding
Number of shares (in thousands), options outstanding	8,346	8,713	10,938	7,488
Weighted average remaining contractual life (in years), options outstanding	6 years 10 months 6 days
Weighted average exercise price per share, options outstanding (in dollars per share)	$ 88.55	$ 69.13	$ 52.67	$ 104.50
Aggregate intrinsic value (in millions), options outstanding				$ 238
Number of Shares (in thousands), options exercisable				3,555
Weighted Average Remaining Contractual Life (in years), Options Exercisable	4 years 8 months 15 days
Weighted average exercise price per share, options exercisable (in dollars per share)				$ 85.91
Aggregate intrinsic value (in millions), options exercisable				$ 179
Additional information on stock options and ESPP shares
Weighted average fair value of options granted (in dollars per share)	$ 25.54	$ 20.35	$ 19.39
Total grant date fair value of options vested	$ 37	$ 32	$ 36
Aggregate intrinsic value of options exercised	126	134	191
Total tax benefit for stock option and ESPP share-based compensation	179	86	75
Cash received from option exercises	153	126	154
Cash tax benefits realized related to tax deductions for non-qualified option exercises and disqualifying dispositions under all share-based payment arrangements	46	47	68
Stock Options And Espp
Additional information on stock options and ESPP shares
Share-based compensation expense for stock options and ESPP	52	48	48
Total tax benefit for stock option and ESPP share-based compensation	$ 49	$ 13	$ 11
Employee Stock Option
Additional information on stock options and ESPP shares
Unrecognized compensation cost				$ 85
Weighted average vesting period	2 years 4 months 24 days
Maximum
Stock Options Outstanding
Market price of common stock (in dollars per share)				$ 137.21