Retirement Plans - Schedule of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Aug. 31, 2020	Aug. 31, 2019
Pension Plans [Member] | U.S. Plans [Member]
Net Periodic Benefit Cost
Service cost	$ 213	$ 192
Other retirement plans (income) expense:
Interest cost	240	250
Expected return on plan assets	(446)	(400)
Amortization of prior service credit and other	(2)	(27)
Other retirement plans (income) expense	(208)	(177)
Net periodic benefit cost	5	15
Pension Plans [Member] | International Pension Plans [Member]
Net Periodic Benefit Cost
Service cost	23	24
Other retirement plans (income) expense:
Interest cost	10	11
Expected return on plan assets	(12)	(13)
Amortization of prior service credit and other	(1)
Other retirement plans (income) expense	(3)	(2)
Net periodic benefit cost	20	22
Postretirement Healthcare Plans [Member]
Net Periodic Benefit Cost
Service cost	11	11
Other retirement plans (income) expense:
Interest cost	10	11
Other retirement plans (income) expense	10	11
Net periodic benefit cost	$ 21	$ 22