Fair Value Measurements (Carrying Value And Fair Value Of Long-Term Debt) (Details) (USD $) In Millions, unless otherwise specified	Oct. 31, 2012	Jan. 31, 2012
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including amounts due within one year, Carrying Value	$ 45,422	$ 46,045
Fair Value, Fair Value Disclosure [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, including amounts due within one year, Fair Value	$ 53,897	$ 53,043