Retirement Plans - Schedule of Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2021	May 31, 2020	May 31, 2019
Pension Plans [Member] | U.S. Plans [Member]
Net Periodic Benefit Cost
Service cost	$ 851	$ 768	$ 689
Interest cost	959	1,000	951
Expected return on plan assets	(1,786)	(1,601)	(1,505)
Amortization of prior service credit	(8)	(105)	(118)
Actuarial (gains) losses and other	(1,288)	888	3,537
Net periodic benefit cost	(1,272)	950	3,554
Pension Plans [Member] | International Pension Plans [Member]
Net Periodic Benefit Cost
Service cost	83	96	94
Interest cost	43	43	49
Expected return on plan assets	(52)	(51)	(46)
Amortization of prior service credit	(2)	(2)	(2)
Actuarial (gains) losses and other	(13)	(179)	80
Net periodic benefit cost	59	(93)	175
Postretirement Healthcare Plans [Member]
Net Periodic Benefit Cost
Service cost	44	42	35
Interest cost	39	44	40
Actuarial (gains) losses and other	125	85	265
Net periodic benefit cost	$ 208	$ 171	$ 340