Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Apr. 25, 2020	Jul. 27, 2019
Assets:
Available-for-sale debt investments	$ 18,208	$ 21,660
Marketable equity securities	0	3
U.S. government securities
Assets:
Available-for-sale debt investments	2,610	808
U.S. government agency securities
Assets:
Available-for-sale debt investments	54	169
Corporate debt securities
Assets:
Available-for-sale debt investments	12,377	19,262
Commercial paper
Assets:
Available-for-sale debt investments	1,272
Certificates of deposit
Assets:
Available-for-sale debt investments	228
Fair value, measurements, recurring
Assets:
Marketable equity securities	0	3
Derivative assets	200	89
Total	27,446	31,835
Liabilities:
Derivative liabilities	22	15
Total	22	15
Fair value, measurements, recurring \| U.S. government securities
Assets:
Available-for-sale debt investments	2,610	808
Fair value, measurements, recurring \| U.S. government agency securities
Assets:
Available-for-sale debt investments	54	169
Fair value, measurements, recurring \| Corporate debt securities
Assets:
Available-for-sale debt investments	12,377	19,262
Fair value, measurements, recurring \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,667	1,421
Fair value, measurements, recurring \| Commercial paper
Assets:
Available-for-sale debt investments	1,272	0
Fair value, measurements, recurring \| Certificates of deposit
Assets:
Available-for-sale debt investments	228	0
Fair value, measurements, recurring \| Money market funds
Assets:
Cash equivalents	8,829	10,083
Fair value, measurements, recurring \| Commercial paper
Assets:
Cash equivalents	189	0
Fair value, measurements, recurring \| Certificates of deposit
Assets:
Cash equivalents	20	0
Fair value, measurements, recurring \| Level 1
Assets:
Marketable equity securities	0	3
Derivative assets	0	0
Total	8,829	10,086
Liabilities:
Derivative liabilities	0	0
Total	0	0
Fair value, measurements, recurring \| Level 1 \| U.S. government securities
Assets:
Available-for-sale debt investments	0	0
Fair value, measurements, recurring \| Level 1 \| U.S. government agency securities
Assets:
Available-for-sale debt investments	0	0
Fair value, measurements, recurring \| Level 1 \| Corporate debt securities
Assets:
Available-for-sale debt investments	0	0
Fair value, measurements, recurring \| Level 1 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	0	0
Fair value, measurements, recurring \| Level 1 \| Commercial paper
Assets:
Available-for-sale debt investments	0	0
Fair value, measurements, recurring \| Level 1 \| Certificates of deposit
Assets:
Available-for-sale debt investments	0	0
Fair value, measurements, recurring \| Level 1 \| Money market funds
Assets:
Cash equivalents	8,829	10,083
Fair value, measurements, recurring \| Level 1 \| Commercial paper
Assets:
Cash equivalents	0	0
Fair value, measurements, recurring \| Level 1 \| Certificates of deposit
Assets:
Cash equivalents	0	0
Fair value, measurements, recurring \| Level 2
Assets:
Marketable equity securities	0	0
Derivative assets	200	89
Total	18,617	21,749
Liabilities:
Derivative liabilities	22	15
Total	22	15
Fair value, measurements, recurring \| Level 2 \| U.S. government securities
Assets:
Available-for-sale debt investments	2,610	808
Fair value, measurements, recurring \| Level 2 \| U.S. government agency securities
Assets:
Available-for-sale debt investments	54	169
Fair value, measurements, recurring \| Level 2 \| Corporate debt securities
Assets:
Available-for-sale debt investments	12,377	19,262
Fair value, measurements, recurring \| Level 2 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,667	1,421
Fair value, measurements, recurring \| Level 2 \| Commercial paper
Assets:
Available-for-sale debt investments	1,272	0
Fair value, measurements, recurring \| Level 2 \| Certificates of deposit
Assets:
Available-for-sale debt investments	228	0
Fair value, measurements, recurring \| Level 2 \| Money market funds
Assets:
Cash equivalents	0	0
Fair value, measurements, recurring \| Level 2 \| Commercial paper
Assets:
Cash equivalents	189	0
Fair value, measurements, recurring \| Level 2 \| Certificates of deposit
Assets:
Cash equivalents	$ 20	$ 0

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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