Fair Value Measurements and Concentrations of Credit Risk (Financial Assets Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Millions	Jan. 28, 2017	Jan. 30, 2016
Marketable equity and debt securities	$ 112	$ 132
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Marketable equity and debt securities	20	13
Significant Observable Inputs (Level 2) [Member]
Marketable equity and debt securities	92	119
Significant Unobservable Inputs (Level 3) [Member]
Marketable equity and debt securities	$ 0	$ 0