Stockholders' Equity - Restricted Stock Unit Activity and Related Share-Based Compensation Expense (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2015
Summary of restricted stock unit activity
Nonvested, Number of shares, Beginning Balance (in shares)	9,039	8,916	9,455
Granted (in shares)	3,983	4,072	3,501
Assumed or granted in connection with acquisitions (in shares)			292
Vested (in shares)	(3,121)	(2,392)	(3,155)
Forfeited (in shares)	(1,265)	(1,557)	(1,177)
Nonvested, Number of shares, Ending Balance (in shares)	8,636	9,039	8,916
Weighted Average Grant Date Fair Value
Nonvested, Weighted Average Grant Date Fair Value per share, Beginning Balance (in dollars per share)	$ 82.30	$ 72.48	$ 62.46
Granted (in dollars per share)	119.84	99.30	89.58
Assumed or granted in connection with acquisitions (in dollars per share)			91.87
Vested (in dollars per share)	86.93	78.07	67.00
Forfeited (in dollars per share)	76.75	77.03	62.32
Nonvested, Weighted Average Grant Date Fair Value per share, Ending Balance (in dollars per share)	$ 98.76	$ 82.30	$ 72.48
Total tax benefit related to RSU share-based compensation expense	$ 179	$ 86	$ 75
Restricted Stock Units (RSUs)
Weighted Average Grant Date Fair Value
Total fair market value of shares vested	388	288	282
Share-based compensation for RSUs	274	230	194
Total tax benefit related to RSU share-based compensation expense	130	73	64
Cash tax benefits realized for tax deductions for RSUs	130	$ 92	$ 96
Unrecognized compensation cost	$ 717
Weighted average vesting period	2 years 4 months 24 days