Income Taxes (Details 3) - USD ($) $ in Millions	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Statutory U.S. income tax rate	35.00%	35.00%	35.00%
Effective tax rate	35.50%	36.50%	37.40%
IncomeTax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Taxes computed at federal statutory rate	$ 569	$ 1,280	$ 1,518
State and local income taxes, net of federal benefit	36	90	117
Foreign operations	(43)	(38)	(21)
Other, net	15	2	8
PROVISION FOR INCOME TAXES	$ 577	$ 1,334	$ 1,622