Guarantees and Indemnifications (Details) (USD $) In Millions	May 31, 2011
Guarantees Abstract
Guaranteed Principal Amount Of Special Facility Revenue Bonds	$ 667
Future Principal And Interest Payments For Special Facility Revenue Bonds	886
Portion Of Guaranteed Principal Included In Capital Lease Obligations	116
Portion Of Guaranteed Principal Accounted For As Operating Leases	$ 551