Derivative Financial Instruments (Balance Sheet Classification Of Financial Instruments) (Details) - USD ($) $ in Millions	Oct. 31, 2016	Jan. 31, 2016
Fair value hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	$ 172	$ 173
Net investment hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	532	319
Net investment hedging | Long-term debt
Derivative [Line Items]
Nonderivative hedging instruments	3,142	3,644
Cash flow hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	0	129
Cash flow hedging | Deferred income taxes and other
Derivative [Line Items]
Derivative liabilities	$ 837	$ 738