Stockholders' Equity - Stock-Option Activity and Related Share-Based Compensation Expense (Details) $ / shares in Units, shares in Thousands, $ in Millions	9 Months Ended
	Apr. 30, 2019 USD ($) $ / shares shares
Number of Shares
Options outstanding, beginning balance (in shares) | shares	5,154
Options granted, number of shares (in shares) | shares	64
Options exercised, number of shares (in shares) | shares	(1,642)
Options canceled or expired, number of shares (in shares) | shares	(242)
Options outstanding, ending balance (in shares) | shares	3,334
Weighted Average Exercise Price Per Share
Weighted average exercise price per share, Beginning Balance (in dollars per share) | $ / shares	$ 120.26
Options granted, weighted average exercise price per share (in dollars per share) | $ / shares	225.47
Options exercised, weighted average exercise price per share (in dollars per share) | $ / shares	99.97
Options canceled or expired, weighted average exercise price per share (in dollars per share) | $ / shares	128.42
Weighted average exercise price per share, Ending Balance (in dollars per share) | $ / shares	$ 131.67
Exercisable (in shares) | shares	2,117
Exercisable, Weighted average exercise price per share (in dollars per share) | $ / shares	$ 111.99
Employee Stock Option
Weighted Average Exercise Price Per Share
Unrecognized compensation cost related to non-vested share based compensation expense | $	$ 37
Expected weighted average vesting period to recognize compensation cost related to share based compensation expense, in years	2 years 2 months 12 days