Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	$ (587)	$ (1,531)
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(2,319)
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	17
Balances - End of Period	(2,889)	(1,531)
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	(2,598)
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	0
Balances - End of Period	(2,551)
Derivative Instruments [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Balances - Beginning of Period	129
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	167
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	13
Balances - End of Period	309
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	112
Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax	4
Balances - End of Period	$ (647)