Leases (Details 1) - USD ($) $ in Millions		12 Months Ended
		May 31, 2016	May 31, 2015	May 31, 2014
Operating Leases Rent Expense [Abstract]
Minimum rentals		$ 2,394	$ 2,249	$ 2,154
Contingent rentals	[1]	214	194	197
Operating leases rent expense, total		$ 2,608	$ 2,443	$ 2,351

[1] Contingent rentals are based on equipment usage.