Fair Value Measurements (Notional Amounts And Fair Values Of Interest Rate Swaps) (Details) (USD $) In Millions	Jul. 31, 2011	Jan. 31, 2011
Notional Amount	$ 9,539	$ 9,779
Fair Value Hedges [Member] | Fixed-Rate Interest Rate Swaps [Member]
Notional Amount	3,945	4,445
Fair Value Hedges [Member] | Fixed-Rate Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value	239	267
Net Investment Hedges [Member] | Cross-Currency Interest Rate Swaps [Member]
Notional Amount	1,250	1,250
Net Investment Hedges [Member] | Cross-Currency Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value	210	233
Cash Flow Hedges [Member] | Cross-Currency Interest Rate Swaps [Member]
Notional Amount	3,082	2,902
Cash Flow Hedges [Member] | Cross-Currency Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value	236	238
Cash Flow Hedges [Member] | Floating-Rate Interest Rate Swaps [Member]
Notional Amount	1,262	1,182
Cash Flow Hedges [Member] | Floating-Rate Interest Rate Swaps [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value	(20)	(18)
Fair Value, Inputs, Level 2 [Member]
Fair Value	$ 665	$ 720