Marketable Securities (Details) - USD ($) $ in Millions	Jan. 27, 2019	Jan. 28, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 7,335	$ 6,916
Unrealized Gain	1	2
Unrealized Loss	(12)	(23)
Estimated Fair Value	7,324	6,895
Cash Equivalents	684	3,789
Marketable Securities	6,640	3,106
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,626	1,304
Unrealized Gain	0	0
Unrealized Loss	(6)	(9)
Estimated Fair Value	2,620	1,295
Cash Equivalents	25	0
Marketable Securities	2,595	1,295
Debt securities of United States government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,284	822
Unrealized Gain	0	0
Unrealized Loss	(4)	(7)
Estimated Fair Value	2,280	815
Cash Equivalents	0	0
Marketable Securities	2,280	815
Debt securities issued by the United States Treasury
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,493	577
Unrealized Gain	0	0
Unrealized Loss	(1)	(4)
Estimated Fair Value	1,492	573
Cash Equivalents	176	0
Marketable Securities	1,316	573
Money market funds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	483	3,789
Unrealized Gain	0	0
Unrealized Loss	0	0
Estimated Fair Value	483	3,789
Cash Equivalents	483	3,789
Marketable Securities	0	0
Foreign government bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	209	42
Unrealized Gain	0	0
Unrealized Loss	0	(1)
Estimated Fair Value	209	41
Cash Equivalents	0	0
Marketable Securities	209	41
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	152	254
Unrealized Gain	0	0
Unrealized Loss	(1)	(2)
Estimated Fair Value	151	252
Cash Equivalents	0	0
Marketable Securities	151	252
Mortgage-backed securities issued by United States government-sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	88	128
Unrealized Gain	1	2
Unrealized Loss	0	0
Estimated Fair Value	89	130
Cash Equivalents	0	0
Marketable Securities	$ 89	$ 130

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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