Description of Business and Summary of Significant Accounting Policies - Schedule of Depreciable Lives and Net Book Value of Our Property and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2019	May 31, 2018
Property Plant And Equipment [Line Items]
Net property and equipment	$ 30,429	$ 28,154
Wide-body Aircraft and Related Equipment [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	15 to 30 years
Net property and equipment	$ 11,975	10,463
Narrow-body and Feeder Aircraft and Related Equipment [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	5 to 18 years
Net property and equipment	$ 2,696	2,908
Package Handling and Ground Support Equipment [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	3 to 30 years
Net property and equipment	$ 4,157	4,028
Information Technology [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	2 to 10 years
Net property and equipment	$ 1,553	1,277
Vehicles And Trailers [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	3 to 15 years
Net property and equipment	$ 4,042	3,747
Facilities and Other Property [Member]
Property Plant And Equipment [Line Items]
Depreciable lives range	2 to 40 years
Net property and equipment	$ 6,006	$ 5,731