Marketable Securities - Contractual Maturity (Details) - USD ($) $ in Millions	Oct. 28, 2018	Jan. 28, 2018
Amortized Cost
Less than 1 year	$ 5,537	$ 5,381
Due in 1 - 5 years	1,923	1,500
Mortgage-backed securities issued by United States government-sponsored enterprises not due at a single maturity date	25	35
Amortized Cost	7,485	6,916
Estimated Fair Value
Less than 1 year	5,524	5,375
Due in 1 - 5 years	1,923	1,485
Mortgage-backed securities issued by United States government-sponsored enterprises not due at a single maturity date	25	35
Estimated Fair Value	$ 7,472	$ 6,895