Derivative Financial Instruments (Balance Sheet Classification Of Financial Instruments) (Details) - USD ($) $ in Millions	Jul. 31, 2015	Jan. 31, 2015
Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Assets	$ 11	$ 12
Derivative Liabilities	22
Fair Value Hedging [Member] | Other Assets and Deferred Charges [Member]
Derivative [Line Items]
Derivative Assets	11	12
Fair Value Hedging [Member] | Deferred Income Taxes and Other [Member]
Derivative [Line Items]
Derivative Liabilities	22
Net Investment Hedging [Member]
Derivative [Line Items]
Derivative Assets	154	207
Nonderivative Hedging Instruments	3,981	4,616
Net Investment Hedging [Member] | Other Assets and Deferred Charges [Member]
Derivative [Line Items]
Derivative Assets	154	207
Net Investment Hedging [Member] | Long term debt due within one year (hedged item) [Member]
Derivative [Line Items]
Nonderivative Hedging Instruments	0	766
Net Investment Hedging [Member] | Long-term Debt [Member]
Derivative [Line Items]
Nonderivative Hedging Instruments	3,981	3,850
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Assets	343	293
Derivative Liabilities	614	611
Cash Flow Hedging [Member] | Other Assets and Deferred Charges [Member]
Derivative [Line Items]
Derivative Assets	343	293
Cash Flow Hedging [Member] | Accrued Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities	0	1
Cash Flow Hedging [Member] | Deferred Income Taxes and Other [Member]
Derivative [Line Items]
Derivative Liabilities	$ 614	$ 610