Derivative Financial Instruments (Balance Sheet Classification Of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012	Oct. 31, 2011
Derivative [Line Items]
Long-term debt due within one year	$ 6,550	$ 1,975	$ 1,470
Long-term debt	38,872	44,070	44,872
Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Assets	92	183
Derivative Liabilities	92	183
Net Investment Hedging [Member]
Derivative [Line Items]
Derivative Assets	234	316
Derivative Liabilities	0	0
Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Assets	248	91
Derivative Liabilities	451	110
PrepaidExpensesandandOther [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Assets	55	2
OtherAssetsandDeferredCharges [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Assets	37	181
OtherAssetsandDeferredCharges [Member] | Net Investment Hedging [Member]
Derivative [Line Items]
Derivative Assets	234	316
OtherAssetsandDeferredCharges [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Assets	248	91
LongTermDebtDueWithinOneYear(HedgedItem) [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Liabilities	55	2
LongTermDebt(HedgedItem) [Member] | Fair Value Hedging [Member]
Derivative [Line Items]
Derivative Liabilities	37	181
Accrued Liabilities [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Liabilities	7
DeferredIncomeTaxesandOther [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Derivative Liabilities	444	110
United Kingdom and Japan [Member] | Net Investment Hedging [Member]
Derivative [Line Items]
Long-term debt due within one year	1,744	785
Long-term debt	6,540	7,546
Liability subtotal	$ 8,284	$ 8,331