Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Oct. 31, 2019	Jul. 31, 2019	Apr. 30, 2019
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	$ 81,197	$ 74,110	$ 81,552	$ 77,131	$ 74,910	$ 79,634
Ending balance	87,504	81,197	74,110	78,307	77,131	74,910
Currency  Translation and Other
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(14,837)	(15,083)	(11,827)	(11,777)	(11,612)	(12,085)
Other comprehensive income (loss) before reclassifications	1,153	246	(3,256)	(995)	(165)	496
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0	0	(23)
Ending balance	(13,684)	(14,837)	(15,083)	(12,772)	(11,777)	(11,612)
Net Investment Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	1,483	1,674	1,517	1,643	1,503	1,395
Other comprehensive income (loss) before reclassifications	(1)	(191)	157	(113)	140	108
Amounts reclassified from accumulated other comprehensive income (loss)	0	0	0	0	0	0
Ending balance	1,482	1,483	1,674	1,530	1,643	1,503
Cash Flow Hedges
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(505)	(818)	(539)	(429)	(271)	(140)
Other comprehensive income (loss) before reclassifications	(13)	303	(295)	(12)	(172)	(145)
Amounts reclassified from accumulated other comprehensive income (loss)	(13)	(10)	16	0	(14)	14
Ending balance	(505)	(505)	(818)	(441)	(429)	(271)
Minimum Pension  Liability
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(1,925)	(1,941)	(1,956)	(707)	(711)	(712)
Other comprehensive income (loss) before reclassifications	(3)	(2)	(4)	6	(5)	(7)
Amounts reclassified from accumulated other comprehensive income (loss)	(19)	(18)	19	(2)	(9)	8
Ending balance	(1,909)	(1,925)	(1,941)	(699)	(707)	(711)
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income Loss [Line Items]
Beginning balance	(15,784)	(16,168)	(12,805)	(11,270)	(11,091)	(11,542)
Other comprehensive income (loss) before reclassifications	1,136	356	(3,398)	(1,114)	(202)	452
Amounts reclassified from accumulated other comprehensive income (loss)	(32)	(28)	35	(2)	(23)	(1)
Ending balance	$ (14,616)	$ (15,784)	$ (16,168)	$ (12,382)	$ (11,270)	$ (11,091)