Program Development Costs (Details) (USD $) In Millions, unless otherwise specified	Aug. 31, 2014	May 31, 2014
Program Development Costs
Net costs capitalized associated with the engineering and development of the cargo system, current and noncurrent	$ 141.2	$ 139.8
Net costs capitalized associated with the engineering and development of the cargo system, current	29.8	27.6
Net costs capitalized associated with the engineering and development of the cargo system, non-current	$ 111.4	$ 112.2