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, 2018 USD ($) $ / shares shares
Number of Shares
Nonvested at beginning of period (in shares) | shares	8,636
Granted, Number of shares (in shares) | shares	431
Unregistered restricted stock granted in connection with acquisitions (in shares) | shares	75
Vested, Number of Shares (in shares) | shares	(840)
Forfeited, Number of Shares (in shares) | shares	(723)
Nonvested at end of period (in shares) | shares	7,579
Weighted Average Grant Date Fair Value
Nonvested, Weighted Average Grant Date Fair Value, at beginning of period (in dollars per shares) | $ / shares	$ 98.76
Granted, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	149.35
Unregistered restricted stock granted in connection with acquisitions (in dollars per share) | $ / shares	163.00
Vested, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	72.58
Forfeited, Weighted Average Grant Date Fair Value (in dollars per shares) | $ / shares	86.02
Nonvested, Weighted Average Grant Date Fair Value, at end of period (in dollars per shares) | $ / shares	$ 106.39
Unrecognized compensation cost related to non-vested RSUs | $	$ 570
Weighted average vesting period, in years	2 years 1 month 6 days