Income Taxes - Schedule of Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	May 31, 2021	May 31, 2020
Components Of Deferred Tax Assets And Liabilities [Abstract]
Property, equipment, leases and intangibles	$ 4,248	$ 3,819
Employee benefits	1,178	1,448
Self-insurance accruals	799	647
Other	497	579
Net operating loss/credit carryforwards	934	1,262
Valuation allowances	(382)	(450)
Deferred Tax Assets, Net	7,274	7,305
Property, equipment, leases and intangibles	9,731	8,745
Other	52	375
Deferred Tax Liabilities	$ 9,783	$ 9,120