Marketable Securities - Unrealized Losses Aggregated by Investment Category (Details) $ in Millions	Jan. 27, 2019 USD ($)
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	$ 3,604
Less than 12 Months, Gross Unrealized Losses	(4)
12 Months or Greater, Fair Value	1,362
12 Months or Greater, Gross Unrealized Losses	(8)
Estimated Fair Value	4,966
Gross Unrealized Losses	(12)
Debt securities of United States government agencies
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	1,674
Less than 12 Months, Gross Unrealized Losses	(1)
12 Months or Greater, Fair Value	401
12 Months or Greater, Gross Unrealized Losses	(3)
Estimated Fair Value	2,075
Gross Unrealized Losses	(4)
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	915
Less than 12 Months, Gross Unrealized Losses	(3)
12 Months or Greater, Fair Value	649
12 Months or Greater, Gross Unrealized Losses	(3)
Estimated Fair Value	1,564
Gross Unrealized Losses	(6)
Debt securities issued by the United States Treasury
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	1,015
Less than 12 Months, Gross Unrealized Losses	0
12 Months or Greater, Fair Value	161
12 Months or Greater, Gross Unrealized Losses	(1)
Estimated Fair Value	1,176
Gross Unrealized Losses	(1)
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Less than 12 Months, Fair Value	0
Less than 12 Months, Gross Unrealized Losses	0
12 Months or Greater, Fair Value	151
12 Months or Greater, Gross Unrealized Losses	(1)
Estimated Fair Value	151
Gross Unrealized Losses	$ (1)