Derivative Financial Instruments (Balance Sheet Classification Of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Apr. 30, 2013	Jan. 31, 2013
Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Assets	$ 23	$ 60
Derivative Liabilities	0	0
Fair Value Hedging [Member] | PrepaidExpensesandandOther [Member]
Derivative [Line Items]
Derivative Assets	11	29
Fair Value Hedging [Member] | OtherAssetsandDeferredCharges [Member]
Derivative [Line Items]
Derivative Assets	12	31
Net Investment Hedging [Member]
Derivative [Line Items]
Derivative Assets	236	223
Derivative Liabilities	0	0
Nonderivative Hedging Instruments	6,688	6,963
Net Investment Hedging [Member] | OtherAssetsandDeferredCharges [Member]
Derivative [Line Items]
Derivative Assets	236	223
Net Investment Hedging [Member] | LongTermDebtDueWithinOneYear(HedgedItem) [Member]
Derivative [Line Items]
Nonderivative Hedging Instruments	767	818
Net Investment Hedging [Member] | Long-term Debt [Member]
Derivative [Line Items]
Nonderivative Hedging Instruments	5,921	6,145
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Assets	241	327
Derivative Liabilities	117	95
Cash Flow Hedging [Member] | OtherAssetsandDeferredCharges [Member]
Derivative [Line Items]
Derivative Assets	241	327
Cash Flow Hedging [Member] | Accrued Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities	2	4
Cash Flow Hedging [Member] | DeferredIncomeTaxesandOther [Member]
Derivative [Line Items]
Derivative Liabilities	$ 115	$ 91