Accumulated Other Comprehensive Income (Loss) (Details) $ in Millions	3 Months Ended
	Apr. 30, 2016 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	$ (11,597)
Other comprehensive income (loss) before reclassifications	600
Amounts reclassified from accumulated other comprehensive income (loss)	2
Balances - end of period	(10,995)
Currency translation and other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(11,690)
Other comprehensive income (loss) before reclassifications	636
Balances - end of period	(11,054)
Net investment hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	1,022
Other comprehensive income (loss) before reclassifications	(78)
Balances - end of period	944
Cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(336)
Other comprehensive income (loss) before reclassifications	139
Amounts reclassified from accumulated other comprehensive income (loss)	4
Balances - end of period	(193)
Minimum pension liability
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(593)
Other comprehensive income (loss) before reclassifications	(97)
Amounts reclassified from accumulated other comprehensive income (loss)	(2)
Balances - end of period	$ (692)