Goodwill and Intangible Assets, Net of Accumulated Amortization (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013	May 31, 2013
Goodwill and Intangible Assets, Net of Accumulated Amortization (Textual)
Goodwill	$ 540.0		$ 540.0		$ 533.9
Amortization expense relating to intangible assets	$ 4.2	$ 4.9	$ 11.7	$ 14.3