Retirement Plans - Schedule of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Other retirement plans expense (income):
MTM net loss	$ 260	$ 52	$ 260	$ 52
Pension Plans [Member] | U.S. Plans [Member]
Net Periodic Benefit Cost
Service cost	208	212	416	425
Other retirement plans expense (income):
Interest cost	255	239	511	479
Expected return on plan assets	(477)	(446)	(955)	(892)
Amortization of prior service credit and other	(2)	(2)	(4)	(4)
MTM net loss	36		36
Other retirement plans (income) expense	(188)	(209)	(412)	(417)
Net periodic benefit cost	20	3	4	8
Pension Plans [Member] | International Pension Plans [Member]
Net Periodic Benefit Cost
Service cost	14	26	29	49
Other retirement plans expense (income):
Interest cost	7	11	19	21
Expected return on plan assets	(6)	(13)	(20)	(25)
Amortization of prior service credit and other	(1)		(1)	(1)
MTM net loss	224	52	224	52
Other retirement plans (income) expense	224	50	222	47
Net periodic benefit cost	238	76	251	96
Postretirement Healthcare Plans [Member]
Net Periodic Benefit Cost
Service cost	12	11	24	22
Other retirement plans expense (income):
Interest cost	11	9	21	19
Other retirement plans (income) expense	11	9	21	19
Net periodic benefit cost	$ 23	$ 20	$ 45	$ 41