Fair Value Measurements (Notional Amounts And Fair Values Of Interest Rate Swaps) (Details) - USD ($) $ in Millions	Apr. 30, 2020	Jan. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	$ 11,716	$ 11,817
Fair value hedging | Interest Rate Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	4,000	4,000
Net investment hedging | Cross-currency swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	3,750	3,750
Cash flow hedges | Cross-currency swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	3,966	4,067
Recurring | Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	(361)	(144)
Recurring | Fair value hedging | Interest Rate Swap | Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	201	97
Recurring | Net investment hedging | Cross-currency swaps | Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	593	455
Recurring | Cash flow hedges | Cross-currency swaps | Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ (1,155)	$ (696)