Goodwill and Other Intangibles (Details) - Schedule of other intangible assets subject to amortization (Parentheticals) (USD $) In Millions, unless otherwise specified	Aug. 31, 2013	May 31, 2013	Aug. 31, 2012
Customer Lists [Member]
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ 2.5	$ 2.3	$ 1.5
Other Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Accumulated amortization	$ 12.4	$ 12.0	$ 10.8