Derivative Financial Instruments (Balance Sheet Classification Of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Jul. 31, 2013	Jan. 31, 2013
Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Assets	$ 16	$ 60
Fair Value Hedging [Member] | PrepaidExpensesandandOther [Member]
Derivative [Line Items]
Derivative Assets	16	29
Fair Value Hedging [Member] | OtherAssetsandDeferredCharges [Member]
Derivative [Line Items]
Derivative Assets		31
Net Investment Hedging [Member]
Derivative [Line Items]
Derivative Assets	192	223
Nonderivative Hedging Instruments	6,615	6,963
Net Investment Hedging [Member] | OtherAssetsandDeferredCharges [Member]
Derivative [Line Items]
Derivative Assets	192	223
Net Investment Hedging [Member] | LongTermDebtDueWithinOneYear(HedgedItem) [Member]
Derivative [Line Items]
Nonderivative Hedging Instruments	765	818
Net Investment Hedging [Member] | Long-term Debt [Member]
Derivative [Line Items]
Nonderivative Hedging Instruments	5,850	6,145
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Assets	540	327
Derivative Liabilities	2	95
Cash Flow Hedging [Member] | OtherAssetsandDeferredCharges [Member]
Derivative [Line Items]
Derivative Assets	540	327
Cash Flow Hedging [Member] | Accrued Liabilities [Member]
Derivative [Line Items]
Derivative Liabilities		4
Cash Flow Hedging [Member] | DeferredIncomeTaxesandOther [Member]
Derivative [Line Items]
Derivative Liabilities	$ 2	$ 91