Accumulated Other Comprehensive Income (Loss) (Details) $ in Millions	3 Months Ended
	Apr. 30, 2017 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	$ (14,232)
Other comprehensive income (loss) before reclassifications	1,273
Amounts reclassified from accumulated other comprehensive income (loss)	5
Balances - end of period	(12,954)
Currency translation and other
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(14,507)
Other comprehensive income (loss) before reclassifications	877
Amounts reclassified from accumulated other comprehensive income (loss)	0
Balances - end of period	(13,630)
Unrealized gain on available-for-sale securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	145
Other comprehensive income (loss) before reclassifications	481
Amounts reclassified from accumulated other comprehensive income (loss)	0
Balances - end of period	626
Net investment hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	1,435
Other comprehensive income (loss) before reclassifications	(113)
Amounts reclassified from accumulated other comprehensive income (loss)	0
Balances - end of period	1,322
Cash flow hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(315)
Other comprehensive income (loss) before reclassifications	21
Amounts reclassified from accumulated other comprehensive income (loss)	7
Balances - end of period	(287)
Minimum pension liability
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balances - beginning of period	(990)
Other comprehensive income (loss) before reclassifications	7
Amounts reclassified from accumulated other comprehensive income (loss)	(2)
Balances - end of period	$ (985)