Fair Value Measurements - Recurring Basis (Details) - USD ($) $ in Millions	Apr. 30, 2019	Jul. 31, 2018
Assets:
Cash equivalents, primarily time deposits, savings deposit accounts, and money market funds	$ 2,946	$ 1,464
Available-for-sale debt securities:
Available-for-sale debt securities	600	452
Fair value, measurements, recurring
Assets:
Cash equivalents, primarily time deposits, savings deposit accounts, and money market funds	2,416	1,143
Available-for-sale debt securities:
Available-for-sale debt securities	600	452
Total assets measured at fair value on a recurring basis	3,016	1,595
Fair value, measurements, recurring \| Level 1
Assets:
Cash equivalents, primarily time deposits, savings deposit accounts, and money market funds	2,416	1,143
Available-for-sale debt securities:
Available-for-sale debt securities	0	0
Total assets measured at fair value on a recurring basis	2,416	1,143
Fair value, measurements, recurring \| Level 2
Assets:
Cash equivalents, primarily time deposits, savings deposit accounts, and money market funds	0	0
Available-for-sale debt securities:
Available-for-sale debt securities	600	452
Total assets measured at fair value on a recurring basis	600	452
Fair value, measurements, recurring \| Level 3
Assets:
Cash equivalents, primarily time deposits, savings deposit accounts, and money market funds	0	0
Available-for-sale debt securities:
Available-for-sale debt securities	0	0
Total assets measured at fair value on a recurring basis	0	0
Municipal bonds \| Fair value, measurements, recurring
Available-for-sale debt securities:
Available-for-sale debt securities	5	31
Municipal bonds \| Fair value, measurements, recurring \| Level 1
Available-for-sale debt securities:
Available-for-sale debt securities	0	0
Municipal bonds \| Fair value, measurements, recurring \| Level 2
Available-for-sale debt securities:
Available-for-sale debt securities	5	31
Municipal bonds \| Fair value, measurements, recurring \| Level 3
Available-for-sale debt securities:
Available-for-sale debt securities	0	0
Corporate notes \| Fair value, measurements, recurring
Available-for-sale debt securities:
Available-for-sale debt securities	570	412
Corporate notes \| Fair value, measurements, recurring \| Level 1
Available-for-sale debt securities:
Available-for-sale debt securities	0	0
Corporate notes \| Fair value, measurements, recurring \| Level 2
Available-for-sale debt securities:
Available-for-sale debt securities	570	412
Corporate notes \| Fair value, measurements, recurring \| Level 3
Available-for-sale debt securities:
Available-for-sale debt securities	0	0
U.S. agency securities \| Fair value, measurements, recurring
Available-for-sale debt securities:
Available-for-sale debt securities	25	9
U.S. agency securities \| Fair value, measurements, recurring \| Level 1
Available-for-sale debt securities:
Available-for-sale debt securities	0	0
U.S. agency securities \| Fair value, measurements, recurring \| Level 2
Available-for-sale debt securities:
Available-for-sale debt securities	25	9
U.S. agency securities \| Fair value, measurements, recurring \| Level 3
Available-for-sale debt securities:
Available-for-sale debt securities	$ 0	$ 0

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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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).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109979856&loc=d3e26610-111562

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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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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