Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Apr. 30, 2013	Apr. 30, 2012
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	$ (587)	$ (463)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1,393)
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	12
Balances - End of Period	(1,968)	(463)
Currency Translation And Other [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	47
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1,408)
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	0
Balances - End of Period	(1,361)
Derivative Instruments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	129
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(91)
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	10
Balances - End of Period	48
Minimum Pension Liability [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	(763)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	106
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	2
Balances - End of Period	$ (655)