Income Taxes and Other Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014	May 31, 2015
Income Tax And Non Income Tax Disclosure [Abstract]
Effective Income Tax Rate, Annualized, Percent					40.00%
Effective Income Tax Rate Reconciliation, Percent	38.40%		43.70%
Tax settlement	$ 0	$ 0	$ 2.9	$ 0