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, 2020 USD ($) $ / shares shares
Number of Shares
Options granted, number of shares (in shares)	0
Employee Stock Option
Number of Shares
Options outstanding, beginning balance (in shares)	2,681
Options granted, number of shares (in shares)	0
Options exercised, number of shares (in shares)	(402)
Options canceled or expired, number of shares (in shares)	(23)
Options outstanding, ending balance (in shares)	2,256
Weighted Average Exercise Price Per Share
Weighted average exercise price per share, beginning balance (in dollars per share) | $ / shares	$ 185.83
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	121.96
Options canceled or expired, weighted average exercise price per share (in dollars per share) | $ / shares	244.47
Weighted average exercise price per share, ending balance (in dollars per share) | $ / shares	$ 196.64
Exercisable (in shares)	1,452
Exercisable, weighted average exercise price per share (in dollars per share) | $ / shares	$ 150.72
Unrecognized compensation cost related to non-vested share based compensation expense | $	$ 52
Expected weighted average vesting period to recognize compensation cost related to share based compensation expense, in years	3 years 1 month 6 days