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	9 Months Ended
	Apr. 30, 2019 USD ($) $ / shares shares
Number of Shares
Nonvested at beginning of period (in shares) | shares	7,383
Granted (in shares) | shares	490
Vested (in shares) | shares	(1,572)
Forfeited (in shares) | shares	(812)
Nonvested at end of period (in shares) | shares	5,489
Weighted Average Grant Date Fair Value
Nonvested, Weighted Average Grant Date Fair Value, at beginning of period (in dollars per shares) | $ / shares	$ 131.50
Granted, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	223.74
Vested, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	111.48
Forfeited, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	106.42
Nonvested, Weighted Average Grant Date Fair Value, at end of period (in dollars per shares) | $ / shares	$ 149.19
Unrecognized compensation cost related to non-vested RSUs | $	$ 578
Weighted average vesting period, in years	2 years 6 months