Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Apr. 30, 2014	Apr. 30, 2013
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	$ (2,996)	$ (1,968)
Other Comprehensive Income (Loss) Before Reclassifications	284
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	0
Balances - End of Period	(2,712)	(1,968)
Currency Translation And Other [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	(2,722)
Other Comprehensive Income (Loss) Before Reclassifications	276
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	0
Balances - End of Period	(2,446)
Derivative Instruments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	336
Other Comprehensive Income (Loss) Before Reclassifications	2
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	2
Balances - End of Period	340
Minimum Pension Liability [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	(610)
Other Comprehensive Income (Loss) Before Reclassifications	6
Amounts Reclassified from Accumulated Other Comprehensive Income (Loss)	(2)
Balances - End of Period	$ (606)