Income Taxes (Details 6) - USD ($) $ in Millions	May 31, 2016	May 31, 2015
Components Of Deferred Tax Assets [Abstract]
Property, equipment, leases and intangibles	$ 129	$ 93
Employee benefits	2,453	2,029
Self-insurance accruals	681	607
Other	528	477
Net operating loss/credit carryforwards	925	326
Valuation allowances	(738)	(224)
Deferred Tax Assets, Net	$ 3,978	$ 3,308