Income Taxes - Schedule of Reconciliation of Total Income Tax Expense and Amount Computed by Statutory Federal Income Tax Rate to Income Before Taxes (Details) - USD ($) $ in Millions	12 Months Ended
	May 31, 2017	May 31, 2016	May 31, 2015
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Taxes computed at federal statutory rate	$ 1,603	$ 959	$ 569
State and local income taxes, net of federal benefit	99	33	36
Foreign operations	(87)	(50)	(43)
Legal entity restructuring		(76)
TNT Express integration/acquisition costs	25	40
Other, net	(58)	14	15
Provision for Income Taxes, Total	$ 1,582	$ 920	$ 577
Effective Tax Rate	34.60%	33.60%	35.50%