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, 2019 USD ($) $ / shares shares
Number of Shares
Nonvested at beginning of period (in shares) | shares	5,683
Granted (in shares) | shares	228
Vested (in shares) | shares	(416)
Forfeited (in shares) | shares	(334)
Nonvested at end of period (in shares) | shares	5,161
Weighted Average Grant Date Fair Value
Nonvested, Weighted Average Grant Date Fair Value, at beginning of period (in dollars per shares) | $ / shares	$ 186.22
Granted, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	270.18
Vested, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	138.05
Forfeited, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	112.51
Nonvested, Weighted Average Grant Date Fair Value, at end of period (in dollars per shares) | $ / shares	$ 198.57
Unrecognized compensation cost related to non-vested RSUs | $	$ 879
Weighted average vesting period, in years	3 years