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, 2020	Jul. 31, 2019	Jul. 31, 2018
Summary of restricted stock unit activity
Nonvested, Number of shares, Beginning Balance (in shares)	5,683	7,383	8,636
Granted (in shares)	2,657	2,452	2,828
Unregistered restricted stock granted in connection with acquisitions (in shares)			75
Vested (in shares)	(2,039)	(3,123)	(2,960)
Forfeited (in shares)	(637)	(1,029)	(1,196)
Nonvested, Number of shares, Ending Balance (in shares)	5,664	5,683	7,383
Weighted Average Grant Date Fair Value
Nonvested, Weighted Average Grant Date Fair Value per share, Beginning Balance (in dollars per share)	$ 186.22	$ 131.50	$ 98.76
Granted (in dollars per share)	271.80	245.40	185.53
Unregistered restricted stock granted in connection with acquisitions (in dollars per share)			163.00
Vested (in dollars per share)	180.40	129.31	105.71
Forfeited (in dollars per share)	154.91	107.40	88.59
Nonvested, Weighted Average Grant Date Fair Value per share, Ending Balance (in dollars per share)	$ 231.97	$ 186.22	$ 131.50
Total tax benefit related to RSU share-based compensation expense	$ 173	$ 200	$ 199
Restricted Stock Units (RSUs)
Weighted Average Grant Date Fair Value
Total fair market value of shares vested	620	676	527
Share-based compensation for RSUs	382	351	326
Total tax benefit related to RSU share-based compensation expense	134	141	143
Cash tax benefits realized for tax deductions for RSUs	139	$ 150	$ 142
Unrecognized compensation cost	$ 1,200
Weighted average vesting period	3 years 2 months 12 days