Retirement Plans - Schedule of MTM Adjustments (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2022	May 31, 2021	May 31, 2020
Actuarial Gain Loss By Component Pre Tax [Abstract]
Actual versus expected return on assets	$ 5,109	$ (1,712)	$ (2,024)
Discount rate change	(4,486)	(397)	2,997
Demographic experience:
Current year actuarial loss	504	302	50
Change in future assumptions	314	685	(229)
Termination of TNT Express Netherlands pension plan	224
Pension plan amendments, including curtailment gains	(87)	(54)
Total MTM (gain) loss	$ 1,578	$ (1,176)	$ 794