Derivatives (Balance Sheet Classification Of Derivatives) (Details) - USD ($) $ in Millions	Jan. 31, 2019	Jan. 31, 2018
Fair value hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	$ 0	$ 0
Fair value hedging | Deferred income taxes and other
Derivative [Line Items]
Derivative liabilities	78	91
Net investment hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	334	208
Net investment hedging | Long-term debt
Derivative [Line Items]
Nonderivative hedging instruments	3,863	4,041
Cash flow hedging | Other assets and deferred charges
Derivative [Line Items]
Derivative assets	78	300
Cash flow hedging | Deferred income taxes and other
Derivative [Line Items]
Derivative liabilities	$ 350	$ 95