Marketable Securities - Amortized Cost and Estimated Fair Value of Cash Equivalents and Marketable Securities (Details) - USD ($) $ in Millions	Jan. 27, 2019	Jan. 28, 2018
Amortized Cost
Less than one year	$ 5,042	$ 5,381
Due in 1 - 5 years	2,271	1,500
Mortgage-backed securities issued by United States government-sponsored enterprises not due at a single maturity date	22	35
Amortized Cost	7,335	6,916
Estimated Fair Value
Less than one year	5,034	5,375
Due in 1 - 5 years	2,268	1,485
Mortgage-backed securities issued by United States government-sponsored enterprises not due at a single maturity date	22	35
Estimated Fair Value	$ 7,324	$ 6,895

Amortized cost of 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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-Publisher FASB
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