Retirement Plans - Reconciliation of Changes In Pension And Postretirement Healthcare Plans Benefit Obligations And Fair Value Of Assets (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
U.S. Plans [Member]
Change in Plan Assets
Company contributions	$ 300	$ 1,000
Pension Plans [Member]
Changes in PBO and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year	32,441
PBO/APBO at the end of year	34,034	32,441
Change in Plan Assets
Balance at beginning of year	28,691
Balance at end of year	31,918	28,691
Funded Status of the Plans	(2,116)	(3,750)
Pension Plans [Member] | U.S. Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation (“ABO”)	30,455	29,272
Changes in PBO and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year	30,199	26,554
Service cost	851	768	$ 689
Interest cost	959	1,000	951
Actuarial loss (gain)	362	2,817
Benefits paid	(948)	(940)
PBO/APBO at the end of year	31,423	30,199	26,554
Change in Plan Assets
Balance at beginning of year	26,978	23,320
Actual return on plan assets	3,436	3,530
Company contributions	319	1,068
Benefits paid	(948)	(940)
Balance at end of year	29,785	26,978	23,320
Funded Status of the Plans	(1,638)	(3,221)
Amount Recognized in the Balance Sheet at May 31:
Current pension, postretirement healthcare and other benefit obligations	(41)	(38)
Noncurrent pension, postretirement healthcare and other benefit obligations	(1,597)	(3,183)
Net amount recognized	(1,638)	(3,221)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service (credit) cost and other	(61)	(68)
Pension Plans [Member] | International Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accumulated Benefit Obligation (“ABO”)	2,417	2,012
Changes in PBO and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year	2,242	2,301
Service cost	83	96	94
Interest cost	43	43	49
Actuarial loss (gain)	105	(87)
Benefits paid	(53)	(41)
Settlements	(11)	(6)
Other	202	(64)
PBO/APBO at the end of year	2,611	2,242	2,301
Change in Plan Assets
Balance at beginning of year	1,713	1,578
Actual return on plan assets	114	146
Company contributions	142	86
Benefits paid	(53)	(41)
Settlements	(11)	(6)
Other	228	(50)
Balance at end of year	2,133	1,713	1,578
Funded Status of the Plans	(478)	(529)
Amount Recognized in the Balance Sheet at May 31:
Noncurrent asset	231	142
Current pension, postretirement healthcare and other benefit obligations	(18)	(17)
Noncurrent pension, postretirement healthcare and other benefit obligations	(691)	(654)
Net amount recognized	(478)	(529)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service (credit) cost and other	(6)	(7)
Postretirement Healthcare Plans [Member]
Changes in PBO and Accumulated Postretirement Benefit Obligation (“APBO”)
PBO/APBO at the beginning of year	1,314	1,221
Service cost	44	42	35
Interest cost	39	44	40
Actuarial loss (gain)	125	85
Benefits paid	(112)	(127)
Other	46	49
PBO/APBO at the end of year	1,456	1,314	$ 1,221
Change in Plan Assets
Company contributions	64	77
Benefits paid	(112)	(127)
Other	48	50
Funded Status of the Plans	(1,456)	(1,314)
Amount Recognized in the Balance Sheet at May 31:
Current pension, postretirement healthcare and other benefit obligations	(110)	(104)
Noncurrent pension, postretirement healthcare and other benefit obligations	(1,346)	(1,210)
Net amount recognized	$ (1,456)	(1,314)
Amounts Recognized in AOCI and not yet reflected in Net Periodic Benefit Cost:
Prior service (credit) cost and other		$ 1