Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Feb. 28, 2014	Feb. 28, 2014	May 31, 2013
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, period increase (decrease)	$ (0.2)	$ 0.4
Unrecognized tax benefits, increase in accrued interest	0.2	0.2
Unrecognized tax benefits could decrease by approximately	0.2	0.2
Balance sheet reclass, change in tax regulations			$ 33.6