Retirement Plans - Schedule of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	Feb. 28, 2022	Feb. 28, 2021
Other retirement plans expense (income):
MTM net loss			$ 260	$ 52
Pension Plans [Member] | U.S. Plans [Member]
Net Periodic Benefit Cost
Service cost	$ 209	$ 213	625	638
Other retirement plans expense (income):
Interest cost	254	240	765	719
Expected return on plan assets	(478)	(447)	(1,433)	(1,339)
Amortization of prior service credit and other	(1)	(2)	(5)	(6)
MTM net loss			36
Other retirement plans (income) expense	(225)	(209)	(637)	(626)
Net periodic benefit cost	(16)	4	(12)	12
Pension Plans [Member] | International Pension Plans [Member]
Net Periodic Benefit Cost
Service cost	14	19	43	68
Other retirement plans expense (income):
Interest cost	8	10	27	31
Expected return on plan assets	(3)	(13)	(23)	(38)
Amortization of prior service credit and other	(1)		(2)	(1)
MTM net loss			224	52
Other retirement plans (income) expense	4	(3)	226	44
Net periodic benefit cost	18	16	269	112
Postretirement Healthcare Plans [Member]
Net Periodic Benefit Cost
Service cost	12	11	36	33
Other retirement plans expense (income):
Interest cost	10	10	31	29
Other retirement plans (income) expense	10	10	31	29
Net periodic benefit cost	$ 22	$ 21	$ 67	$ 62