Fair Value - Assets and Liabilities Measured At Fair Value On Recurring Basis (Details) - USD ($) $ in Millions	Jul. 27, 2019	Jul. 28, 2018
Assets:
Available-for-sale debt investments	$ 21,660	$ 37,009
Marketable equity securities	3	605
Derivative assets	89	2
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	15	74
U.S. government securities
Assets:
Available-for-sale debt investments	808	7,275
U.S. government agency securities
Assets:
Available-for-sale debt investments	169	727
Non-U.S. government and agency securities
Assets:
Available-for-sale debt investments		208
Corporate debt securities
Assets:
Available-for-sale debt investments	19,262	27,364
Recurring
Assets:
Marketable equity securities	3	605
Derivative assets	89	2
Total	31,835	44,506
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	15	74
Total	15	74
Recurring \| U.S. government securities
Assets:
Available-for-sale debt investments	808	7,275
Recurring \| U.S. government agency securities
Assets:
Available-for-sale debt investments	169	727
Recurring \| Non-U.S. government and agency securities
Assets:
Available-for-sale debt investments	0	208
Recurring \| Corporate debt securities
Assets:
Available-for-sale debt investments	19,262	27,364
Recurring \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,421	1,435
Recurring \| Money market funds
Assets:
Cash equivalents	10,083	6,890
Recurring \| Level 1
Assets:
Marketable equity securities	3	605
Derivative assets	0	0
Total	10,086	7,495
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	0	0
Total	0	0
Recurring \| Level 1 \| U.S. government securities
Assets:
Available-for-sale debt investments	0	0
Recurring \| Level 1 \| U.S. government agency securities
Assets:
Available-for-sale debt investments	0	0
Recurring \| Level 1 \| Non-U.S. government and agency securities
Assets:
Available-for-sale debt investments	0	0
Recurring \| Level 1 \| Corporate debt securities
Assets:
Available-for-sale debt investments	0	0
Recurring \| Level 1 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	0	0
Recurring \| Level 1 \| Money market funds
Assets:
Cash equivalents	10,083	6,890
Recurring \| Level 2
Assets:
Marketable equity securities	0	0
Derivative assets	89	2
Total	21,749	37,011
Liabilities, Fair Value Disclosure [Abstract]
Derivative liabilities	15	74
Total	15	74
Recurring \| Level 2 \| U.S. government securities
Assets:
Available-for-sale debt investments	808	7,275
Recurring \| Level 2 \| U.S. government agency securities
Assets:
Available-for-sale debt investments	169	727
Recurring \| Level 2 \| Non-U.S. government and agency securities
Assets:
Available-for-sale debt investments	0	208
Recurring \| Level 2 \| Corporate debt securities
Assets:
Available-for-sale debt investments	19,262	27,364
Recurring \| Level 2 \| U.S. agency mortgage-backed securities
Assets:
Available-for-sale debt investments	1,421	1,435
Recurring \| Level 2 \| Money market funds
Assets:
Cash equivalents	$ 0	$ 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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