Leases - Schedule of Rent Expense Under Operating Leases (Details) - USD ($) $ in Millions		12 Months Ended
		May 31, 2019	May 31, 2018	May 31, 2017
Operating Leases Rent Expense [Abstract]
Minimum rentals		$ 2,875	$ 2,913	$ 2,814
Contingent rentals	[1]	222	194	178
Operating leases rent expense, total		$ 3,097	$ 3,107	$ 2,992

[1] Contingent rentals are based on equipment usage.