Retirement Plans - Schedule of MTM Adjustments (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2024	May 31, 2023	May 31, 2022
Actuarial Gain Loss By Component Pre Tax [Abstract]
Actual versus expected return on assets	$ (67)	$ 2,492	$ 5,109
Discount rate change	(1,139)	(3,395)	(4,486)
Demographic experience:
Current year actuarial loss	67	142	504
Change in future assumptions	577	110	314
Termination of TNT Express Netherlands pension plan			224
Pension plan amendments, including curtailment gains	1	1	(87)
Total MTM (gain) loss	$ (561)	$ (650)	$ 1,578