Fair Value Measurements (Carrying Value And Fair Value Of Long-Term Debt) (Details) - USD ($) $ in Millions	Jul. 31, 2015	Jan. 31, 2015
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt	$ 42,605	$ 45,680
Fair Value | 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	$ 48,961	$ 56,237