Fair Value Measurements Fair Value Measurements (Securities Narrative) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jul. 29, 2017	Jul. 30, 2016	Apr. 30, 2016	Jul. 29, 2017	Jul. 30, 2016	Jan. 28, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	$ 6	$ 8		$ 6	$ 8	$ 5
Proceeds from Sale of Available-for-sale Securities, Equity			$ 10
Available-for-sale Securities, Gross Realized Gains				0	4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	0	3	0	3
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	6	8		6	8	$ 5
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities, Gross Realized Gains	0	0	$ 4	0	4
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	$ 0	$ 0		$ 0	$ 3