Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Jul. 31, 2020 USD ($) Period_of_time $ / shares shares	Jul. 31, 2019 USD ($) shares	Jul. 31, 2018 USD ($) shares	Aug. 31, 2020 $ / shares	Jul. 31, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased during period (in shares) | $	$ 318	$ 561	$ 272
Common stock dividends, cash paid (in dollars per share) | $ / shares	$ 2.12
Dividends and dividend rights declared | $	$ 562	$ 500	$ 407
Common stock, shares authorized (in shares)	750,000,000	750,000,000
Pool shares reduced for each share granted (in shares)	2.3
Pool shares increased for each share forfeited (in shares)	2.3
Shares available for grant (in shares)	18,047,000	21,058,000	22,791,000		25,164,000
Stock offering period, months, employee stock purchase plans	6 months
Stock accrual period, employee stock purchase plans, number of accrual periods | Period_of_time	2
Stock offering period, number of months in accrual period	3 months
Percentage of lower of the closing price for stock on the first day last day of the offering period	85.00%
Shares issued during period for Employee Stock Purchase Plans (in shares)	449,999	485,011	612,768
Shares available for issuance under Employee Stock Purchase Plan (in shares)	1,456,184
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)	18,000,000.0
Number of years until options vest	7 years
Stock Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Stock Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Restricted Stock Units (RSUs) | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Restricted Stock Units (RSUs) | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	23,800,000
Restated 2005 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)	138,100,000
Restated 2005 Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Pool shares reduced for each share granted (in shares)	1
Number of shares added back to plan when grants are forfeited (in shares)	1
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend per share payable (in dollars per share) | $ / shares				$ 0.59
Current Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program remaining authorized repurchase amount | $	$ 2,400
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchases under stock repurchase programs (in shares)	1,176,000	2,455,000	1,870,000