Long-term Debt (Details) In Millions, unless otherwise specified	9 Months Ended		0 Months Ended				0 Months Ended			0 Months Ended						0 Months Ended
	Oct. 31, 2014 USD ($)	Oct. 31, 2013 USD ($)	Apr. 22, 2014 Debt Securities [Member] USD ($)	Apr. 08, 2014 Debt Securities [Member] USD ($)	Oct. 22, 2014 Debt Securities [Member] USD ($)	Apr. 22, 2014 Debt Securities [Member] 1.000% Debt Issuance, Due 2017 [Domain] USD ($)	Oct. 22, 2014 Debt Securities [Member] 3.300% Debt Issuance, Due 2024 [Domain] USD ($)	Apr. 22, 2014 Debt Securities [Member] 3.300% Debt Issuance, Due 2024 [Domain] USD ($)	Apr. 22, 2014 Debt Securities [Member] 4.300% Debt Issuance, Due 2044 [Domain} USD ($)	Feb. 03, 2014 Debt Securities [Member] 3.000% Debt, Due 2014 [Domain] USD ($)	Apr. 14, 2014 Debt Securities [Member] 1.625% Debt, Due 2014 [Domain] USD ($)	May 15, 2014 Debt Securities [Member] 3.200% Debt, Due 2014 [Domain] USD ($)	Apr. 08, 2014 Euro Member Countries, Euro Debt Securities [Member] EUR (€)	Apr. 08, 2014 Euro Member Countries, Euro Debt Securities [Member] 1.900% Debt Issuance, Due 2022 [Domain] EUR (€)	Apr. 08, 2014 Euro Member Countries, Euro Debt Securities [Member] 2.550% Debt Issuance, Due 2026 [Domain] EUR (€)	Aug. 06, 2014 JAPAN Debt Securities [Member] JPY (¥)
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 2,500		$ 1,500	$ 500	$ 500	$ 1,000	$ 1,000				€ 1,500	€ 850	€ 650
Proceeds from issuance of long-term debt	5,120	7,053	2,500	2,000			508
Debt Instrument, Interest Rate, Stated Percentage						1.00%		3.30%	4.30%	3.00%	1.625%	3.20%		1.90%	2.55%
Payments of long-term debt	$ 3,883	$ 4,943								$ 500	$ 1,000	$ 1,000				¥ 100,000