Income Taxes - Schedule of Significant Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	May 31, 2019	May 31, 2018
Components Of Deferred Tax Assets And Liabilities [Abstract]
Property, equipment, leases and intangibles	$ 592	$ 752
Employee benefits	1,256	595
Self-insurance accruals	585	494
Other	510	416
Net operating loss/credit carryforwards	1,139	1,146
Valuation allowances	(590)	(711)
Deferred Tax Assets, Net	3,492	2,692
Property, equipment, leases and intangibles	4,633	3,663
Employee benefits		31
Other	340	602
Deferred Tax Liabilities	$ 4,973	$ 4,296