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	6 Months Ended
	Jan. 31, 2020 USD ($) $ / shares shares
Number of Shares
Nonvested at beginning of period (in shares) | shares	5,683
Granted (in shares) | shares	372
Vested (in shares) | shares	(734)
Forfeited (in shares) | shares	(434)
Nonvested at end of period (in shares) | shares	4,887
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	268.94
Vested, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	157.39
Forfeited, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	132.98
Nonvested, Weighted Average Grant Date Fair Value, at end of period (in dollars per shares) | $ / shares	$ 201.56
Unrecognized compensation cost related to non-vested RSUs | $	$ 801
Weighted average vesting period, in years	2 years 10 months 24 days