Fair Value Measurements (Notional Amounts And Fair Values Of Interest Rate Swaps) (Details) - Recurring [Member] - USD ($) $ in Millions	Jul. 31, 2015	Jan. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	$ 10,608	$ 6,334
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	(128)	(99)
Fair Value Hedging [Member] | Floating-Rate Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	5,000	500
Fair Value Hedging [Member] | Floating-Rate Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	(11)	12
Net Investment Hedging [Member] | Cross-Currency Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	1,250	1,250
Net Investment Hedging [Member] | Cross-Currency Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	154	207
Cash Flow Hedging [Member] | Cross-Currency Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	4,358	4,329
Cash Flow Hedging [Member] | Cross-Currency Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	(271)	(317)
Cash Flow Hedging [Member] | Fixed-Rate Interest Rate Swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional Amount	0	255
Cash Flow Hedging [Member] | Fixed-Rate Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 0	$ (1)