Fair Value - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Millions	Jan. 25, 2020	Jul. 27, 2019
Assets:
Available-for-sale debt investments	$ 18,587	$ 21,660
Marketable equity securities	0	3
U.S. government securities
Assets:
Available-for-sale debt investments	2,231	808
U.S. government agency securities
Assets:
Available-for-sale debt investments	20	169
Corporate debt securities
Assets:
Available-for-sale debt investments	13,597	19,262
Commercial paper
Assets:
Available-for-sale debt investments	1,052
Certificates of deposit
Assets:
Available-for-sale debt investments	64
Fair value, measurements, recurring
Assets:
Marketable equity securities	0	3
Derivative assets	103	89
Total	25,480	31,835
Liabilities:
Derivative liabilities	15	15
Total	15	15
Fair value, measurements, recurring \| U.S. government securities
Assets:
Available-for-sale debt investments	2,231	808
Fair value, measurements, recurring \| U.S. government agency securities
Assets:
Available-for-sale debt investments	20	169
Fair value, measurements, recurring \| Corporate debt securities
Assets:
Available-for-sale debt investments	13,597	19,262
Fair value, measurements, recurring \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,623	1,421
Fair value, measurements, recurring \| Commercial paper
Assets:
Available-for-sale debt investments	1,052	0
Fair value, measurements, recurring \| Certificates of deposit
Assets:
Available-for-sale debt investments	64	0
Fair value, measurements, recurring \| Money market funds
Assets:
Cash equivalents	6,556	10,083
Fair value, measurements, recurring \| Commercial paper
Assets:
Cash equivalents	216	0
Fair value, measurements, recurring \| Certificates of deposit
Assets:
Cash equivalents	18	0
Fair value, measurements, recurring \| Level 1
Assets:
Marketable equity securities	0	3
Derivative assets	0	0
Total	6,556	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	6,556	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	103	89
Total	18,924	21,749
Liabilities:
Derivative liabilities	15	15
Total	15	15
Fair value, measurements, recurring \| Level 2 \| U.S. government securities
Assets:
Available-for-sale debt investments	2,231	808
Fair value, measurements, recurring \| Level 2 \| U.S. government agency securities
Assets:
Available-for-sale debt investments	20	169
Fair value, measurements, recurring \| Level 2 \| Corporate debt securities
Assets:
Available-for-sale debt investments	13,597	19,262
Fair value, measurements, recurring \| Level 2 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,623	1,421
Fair value, measurements, recurring \| Level 2 \| Commercial paper
Assets:
Available-for-sale debt investments	1,052	0
Fair value, measurements, recurring \| Level 2 \| Certificates of deposit
Assets:
Available-for-sale debt investments	64	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	216	0
Fair value, measurements, recurring \| Level 2 \| Certificates of deposit
Assets:
Cash equivalents	$ 18	$ 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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