Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Nov. 30, 2017	Nov. 30, 2016	Nov. 30, 2017	Nov. 30, 2016	May 31, 2017
Income Tax Disclosure [Abstract]
Unrecognized tax benefits	$ 18.7		$ 18.7		$ 12.6
Effective tax rate	33.30%	34.90%	29.80%	31.50%