Debt (Long-Term Debt Issuances) (Details) (USD $)	9 Months Ended
	Oct. 31, 2011
Debt Instrument [Line Items]
Long-term debt, Principal Amount	$ 5,000,000,000
1.625% Debt Due April 15, 2014 [Member]
Debt Instrument [Line Items]
Long-term debt, Issue Date	2011-04-18
Long-term debt, Maturity Date	Apr. 15, 2014
Long-term debt, Interest Rate	1.625%
Long-term debt, Principal Amount	1,000,000,000
2.800% Debt Due April 15, 2016 [Member]
Debt Instrument [Line Items]
Long-term debt, Issue Date	2011-04-18
Long-term debt, Maturity Date	Apr. 15, 2016
Long-term debt, Interest Rate	2.80%
Long-term debt, Principal Amount	1,000,000,000
4.250% Debt Due April 15, 2021 [Member]
Debt Instrument [Line Items]
Long-term debt, Issue Date	2011-04-18
Long-term debt, Maturity Date	Apr. 15, 2021
Long-term debt, Interest Rate	4.25%
Long-term debt, Principal Amount	1,000,000,000
5.625% Debt Due April 15, 2041 [Member]
Debt Instrument [Line Items]
Long-term debt, Issue Date	2011-04-18
Long-term debt, Maturity Date	Apr. 15, 2041
Long-term debt, Interest Rate	5.625%
Long-term debt, Principal Amount	$ 2,000,000,000