Long-term Debt (Details) (USD $)	6 Months Ended
	Jul. 31, 2013
Debt Instrument [Line Items]
Proceeds from Issuance of Debt	$ 5,000,000,000
Debt Instrument, Face Amount	5,000,000,000
Debt Instrument, Date of First Required Payment	Oct. 11, 2013
Percentage of Principal Amount Redeemed	100.00%
0.600% Debt due April 11, 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	Apr. 11, 2013
Debt Instrument, Maturity Date	Apr. 11, 2016
Debt Instrument, Interest Rate, Stated Percentage	0.60%
Debt Instrument, Face Amount	1,000,000,000
1.125% Debt due April 11, 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	Apr. 11, 2013
Debt Instrument, Maturity Date	Apr. 11, 2018
Debt Instrument, Interest Rate, Stated Percentage	1.125%
Debt Instrument, Face Amount	1,250,000,000
2.550% Debt due April 11, 2023 [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	Apr. 11, 2013
Debt Instrument, Maturity Date	Apr. 11, 2023
Early Redemption Date	Jan. 11, 2023
Debt Instrument, Interest Rate, Stated Percentage	2.55%
Debt Instrument, Face Amount	1,750,000,000
4.000% Debt due April 11, 2043 [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date	Apr. 11, 2013
Debt Instrument, Maturity Date	Apr. 11, 2043
Early Redemption Date	Oct. 11, 2042
Debt Instrument, Interest Rate, Stated Percentage	4.00%
Debt Instrument, Face Amount	$ 1,000,000,000