Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Jan. 19, 2017 shares	Jul. 31, 2017 USD ($) Period_of_time $ / shares shares	Jul. 31, 2016 USD ($) shares	Jul. 31, 2015 USD ($) shares	Aug. 31, 2017 $ / shares	Jul. 31, 2014 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased during period (in shares) | $		$ 839	$ 2,264	$ 1,245
Common stock dividends, cash paid (in dollars per share) | $ / shares		$ 1.36
Dividends and dividend rights paid | $		$ 353	$ 318	$ 283
Additional shares authorized (in shares)		23,110,000
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)		25,164,000	8,990,000	17,183,000		24,203,000
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)		752,605	882,206	892,632
Shares available for issuance under Employee Stock Purchase Plan (in shares)		3,003,962
Restated 2005 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized (in shares)	23,100,000
Common stock, shares authorized (in shares)		138,100,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for grant (in shares)		25,200,000
Award vesting period (in years)		3 years
Number of years until options vest		7 years
Stock Options | Restated 2005 Plan
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
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, shares authorized (in shares)		23,800,000
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period (in years)		3 years
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend per share payable (in dollars per share) | $ / shares					$ 0.39
Current Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program remaining authorized repurchase amount | $		$ 1,500
Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchases under stock repurchase programs (in shares)		6,900,000	24,816,000	13,809,000