Fair Value Measurements - Schedule of financial assets and liabilities measured at fair value (Details) - USD ($) $ in Millions	Jul. 31, 2021	Jul. 31, 2020
Available-for-sale debt securities:
Total available-for-sale debt securities	$ 1,508	$ 808
Liabilities:
Carrying value	2,048
Municipal bonds
Available-for-sale debt securities:
Total available-for-sale debt securities	38	9
Corporate notes
Available-for-sale debt securities:
Total available-for-sale debt securities	1,400	752
U.S. agency securities
Available-for-sale debt securities:
Total available-for-sale debt securities	70	47
Fair Value, Measurements, Recurring
Assets:
Cash equivalents, primarily money market funds and time deposits	1,660	5,765
Available-for-sale debt securities:
Total available-for-sale debt securities	1,508	808
Total assets measured at fair value on a recurring basis	3,168	6,573
Fair Value, Measurements, Recurring \| Municipal bonds
Available-for-sale debt securities:
Total available-for-sale debt securities	38	9
Fair Value, Measurements, Recurring \| Corporate notes
Available-for-sale debt securities:
Total available-for-sale debt securities	1,400	752
Fair Value, Measurements, Recurring \| U.S. agency securities
Available-for-sale debt securities:
Total available-for-sale debt securities	70	47
Fair Value, Measurements, Recurring \| Level 1
Assets:
Cash equivalents, primarily money market funds and time deposits	1,660	5,765
Available-for-sale debt securities:
Total available-for-sale debt securities	0	0
Total assets measured at fair value on a recurring basis	1,660	5,765
Fair Value, Measurements, Recurring \| Level 1 \| Municipal bonds
Available-for-sale debt securities:
Total available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Corporate notes
Available-for-sale debt securities:
Total available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 1 \| U.S. agency securities
Available-for-sale debt securities:
Total available-for-sale debt securities	0	0
Fair Value, Measurements, Recurring \| Level 2
Assets:
Cash equivalents, primarily money market funds and time deposits	0	0
Available-for-sale debt securities:
Total available-for-sale debt securities	1,508	808
Total assets measured at fair value on a recurring basis	1,508	808
Fair Value, Measurements, Recurring \| Level 2 \| Municipal bonds
Available-for-sale debt securities:
Total available-for-sale debt securities	38	9
Fair Value, Measurements, Recurring \| Level 2 \| Corporate notes
Available-for-sale debt securities:
Total available-for-sale debt securities	1,400	752
Fair Value, Measurements, Recurring \| Level 2 \| U.S. agency securities
Available-for-sale debt securities:
Total available-for-sale debt securities	70	47
Senior Unsecured Notes
Liabilities:
Carrying value	1,990	1,980
Senior Unsecured Notes \| Fair Value, Measurements, Recurring
Liabilities:
Senior unsecured notes	1,986	2,042
Senior Unsecured Notes \| Fair Value, Measurements, Recurring \| Level 1
Liabilities:
Senior unsecured notes	0	0
Senior Unsecured Notes \| Fair Value, Measurements, Recurring \| Level 2
Liabilities:
Senior unsecured notes	$ 1,986	$ 2,042

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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