Stockholders' Equity - Restricted Stock Unit Activity and Related Share-Based Compensation Expense (Details) - Restricted Stock Units (RSUs) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Oct. 31, 2020 USD ($) $ / shares shares
Number of Shares
Nonvested at beginning of period (in shares) | shares	5,664
Granted (in shares) | shares	158
Vested (in shares) | shares	(480)
Forfeited (in shares) | shares	(404)
Nonvested at end of period (in shares) | shares	4,938
Weighted Average Grant Date Fair Value
Nonvested, weighted average grant date fair value, at beginning of period (in dollars per shares) | $ / shares	$ 231.97
Granted, weighted average grant date fair value (in dollars per shares) | $ / shares	322.24
Vested, weighted average grant date fair value (in dollars per shares) | $ / shares	163.73
Forfeited, weighted average grant date fair value (in dollars per shares) | $ / shares	195.55
Nonvested, weighted average grant date fair value, at end of period (in dollars per shares) | $ / shares	$ 244.48
Unrecognized compensation cost related to non-vested RSUs | $	$ 1,100
Weighted average vesting period, in years	3 years