Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Jul. 31, 2020	Apr. 30, 2020	Jul. 31, 2019	Apr. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 74,110	$ 81,552	$ 74,910	$ 79,634
Other comprehensive income (loss) before reclassifications	356	(3,398)	(202)	452
Amounts reclassified from accumulated other comprehensive income (loss)	(28)	35	(23)	(1)
Ending balance	81,197	74,110	77,131	74,910
Currency Translation and Other
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(15,083)	(11,827)	(11,612)	(12,085)
Other comprehensive income (loss) before reclassifications	246	(3,256)	(165)	496
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	(23)
Ending balance	(14,837)	(15,083)	(11,777)	(11,612)
Net Investment Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	1,674	1,517	1,503	1,395
Other comprehensive income (loss) before reclassifications	(191)	157	140	108
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0
Ending balance	1,483	1,674	1,643	1,503
Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(818)	(539)	(271)	(140)
Other comprehensive income (loss) before reclassifications	303	(295)	(172)	(145)
Amounts reclassified from accumulated other comprehensive income (loss)	(10)	16	(14)	14
Ending balance	(505)	(818)	(429)	(271)
Minimum Pension Liability
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(1,941)	(1,956)	(711)	(712)
Other comprehensive income (loss) before reclassifications	(2)	(4)	(5)	(7)
Amounts reclassified from accumulated other comprehensive income (loss)	(18)	19	(9)	8
Ending balance	(1,925)	(1,941)	(707)	(711)
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(16,168)	(12,805)	(11,091)	(11,542)
Ending balance	$ (15,784)	$ (16,168)	$ (11,270)	$ (11,091)