Fair Value Measurements (Notional Amounts And Fair Values Of Interest Rate Swaps) (Details) - USD ($) $ in Millions	Jan. 31, 2020	Jan. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount	$ 11,817	$ 10,423
Receive fixed-rate, pay variable-rate interest rate swaps designated as fair value hedges | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount	4,000	4,000
Receive fixed-rate, pay fixed-rate cross-currency swaps designated as net investment hedges | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount	3,750	2,250
Receive fixed-rate, pay fixed-rate cross-currency swaps designated as cash flow hedges | Cross-currency interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Notional Amount	4,067	4,173
Recurring | Level 2 inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	(144)	(16)
Recurring | Receive fixed-rate, pay fixed-rate cross-currency swaps designated as cash flow hedges | Cross-currency interest rate swaps | Level 2 inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value		(272)
Other long-term assets | Recurring | Receive fixed-rate, pay variable-rate interest rate swaps designated as fair value hedges | Interest Rate Swap [Member] | Level 2 inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	97
Other long-term assets | Recurring | Receive fixed-rate, pay fixed-rate cross-currency swaps designated as net investment hedges | Cross-currency interest rate swaps | Level 2 inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	455	334
Other long-term assets | Recurring | Receive fixed-rate, pay fixed-rate cross-currency swaps designated as cash flow hedges | Cross-currency interest rate swaps | Level 2 inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value		78
Deferred income taxes and other | Recurring | Receive fixed-rate, pay variable-rate interest rate swaps designated as fair value hedges | Interest Rate Swap [Member] | Level 2 inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value		(78)
Deferred income taxes and other | Recurring | Receive fixed-rate, pay fixed-rate cross-currency swaps designated as cash flow hedges | Cross-currency interest rate swaps | Level 2 inputs
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value	$ (696)	$ (350)