Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Millions	Jan. 31, 2021	Jul. 31, 2020
Assets:
Cash equivalents, primarily money market funds and time deposits	$ 1,952	$ 6,442
Available-for-sale debt securities:	986	808
Long-term debt	2,033	2,031
Senior Unsecured Notes
Assets:
Long-term debt	1,990	1,980
Fair value, measurements, recurring
Assets:
Cash equivalents, primarily money market funds and time deposits	327	5,765
Available-for-sale debt securities:	986	808
Total assets measured at fair value on a recurring basis	1,313	6,573
Fair value, measurements, recurring \| Senior Unsecured Notes
Assets:
Senior unsecured notes	2,017	2,042
Fair value, measurements, recurring \| Level 1
Assets:
Cash equivalents, primarily money market funds and time deposits	327	5,765
Available-for-sale debt securities:	0	0
Total assets measured at fair value on a recurring basis	327	5,765
Fair value, measurements, recurring \| Level 1 \| Senior Unsecured Notes
Assets:
Senior unsecured notes	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:	986	808
Total assets measured at fair value on a recurring basis	986	808
Fair value, measurements, recurring \| Level 2 \| Senior Unsecured Notes
Assets:
Senior unsecured notes	2,017	2,042
Fair value, measurements, recurring \| Municipal bonds
Assets:
Available-for-sale debt securities:	34	9
Fair value, measurements, recurring \| Municipal bonds \| Level 1
Assets:
Available-for-sale debt securities:	0	0
Fair value, measurements, recurring \| Municipal bonds \| Level 2
Assets:
Available-for-sale debt securities:	34	9
Fair value, measurements, recurring \| Corporate notes
Assets:
Available-for-sale debt securities:	869	752
Fair value, measurements, recurring \| Corporate notes \| Level 1
Assets:
Available-for-sale debt securities:	0	0
Fair value, measurements, recurring \| Corporate notes \| Level 2
Assets:
Available-for-sale debt securities:	869	752
Fair value, measurements, recurring \| U.S. agency securities
Assets:
Available-for-sale debt securities:	83	47
Fair value, measurements, recurring \| U.S. agency securities \| Level 1
Assets:
Available-for-sale debt securities:	0	0
Fair value, measurements, recurring \| U.S. agency securities \| Level 2
Assets:
Available-for-sale debt securities:	$ 83	$ 47

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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