Stockholders' Equity - Stock-Option Activity and Related Share-Based Compensation Expense (Details) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Oct. 31, 2017 USD ($) $ / shares shares
Number of Shares
Options outstanding, beginning balance (in shares) | shares	7,488
Options granted, number of shares (in shares) | shares	0
Options exercised, number of shares (in shares) | shares	(671)
Options canceled or expired, number of shares (in shares) | shares	(109)
Options outstanding, ending balance (in shares) | shares	6,708
Weighted Average Exercise Price Per Share
Weighted average exercise price per share, Beginning Balance (in dollars per share) | $ / shares	$ 104.50
Options granted, weighted average exercise price per share (in dollars per share) | $ / shares	0
Options exercised, weighted average exercise price per share (in dollars per share) | $ / shares	80.33
Options canceled or expired, weighted average exercise price per share (in dollars per share) | $ / shares	115.17
Weighted average exercise price per share, Ending Balance (in dollars per share) | $ / shares	$ 106.74
Exercisable (in shares) | shares	3,262
Exercisable, Weighted average exercise price per share (in dollars per share) | $ / shares	$ 88.83
Employee Stock Option
Weighted Average Exercise Price Per Share
Unrecognized compensation cost related to non-vested share based compensation expense | $	$ 73
Expected weighted average vesting period to recognize compensation cost related to share based compensation expense, in years	2 years 2 months 12 days