Leases (Details 2) (USD $) In Millions	12 Months Ended
	May 31, 2011		May 31, 2010		May 31, 2009
Operating Leases Rent Expense Abstract
Minimum rentals	$ 2,025		$ 2,001		$ 2,047
Contingent rentals	193	[1]	152	[1]	181	[1]
Operating leases rent expense, total	$ 2,218		$ 2,153		$ 2,228

[1] Contingent rentals are based on equipment usage.