Derivative Financial Instruments (Balance Sheet Classification Of Financial Instruments) (Details) - USD ($) $ in Millions	Oct. 31, 2015	Jan. 31, 2015
Fair value hedging
Derivative [Line Items]
Derivative assets	$ 91	$ 12
Derivative liabilities	0
Fair value hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	91	12
Fair value hedging | Deferred income taxes and other
Derivative [Line Items]
Derivative liabilities	0
Net investment hedging
Derivative [Line Items]
Derivative assets	192	207
Nonderivative hedging instruments	3,940	4,616
Net investment hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	192	207
Net investment hedging | Long term debt due within one year (hedged item)
Derivative [Line Items]
Nonderivative hedging instruments	0	766
Net investment hedging | Long-term debt
Derivative [Line Items]
Nonderivative hedging instruments	3,940	3,850
Cash flow hedging
Derivative [Line Items]
Derivative assets	292	293
Derivative liabilities	662	611
Cash flow hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	292	293
Cash flow hedging | Accrued liabilities
Derivative [Line Items]
Derivative liabilities	0	1
Cash flow hedging | Deferred income taxes and other
Derivative [Line Items]
Derivative liabilities	$ 662	$ 610