Investment Income, Net (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	May 31, 2016	Feb. 29, 2016	Nov. 30, 2015	Aug. 31, 2015	May 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May 31, 2016	May 31, 2015	May 31, 2014
Investment Income, Net [Abstract]
Interest income on corporate funds									$ 8.4	$ 7.8	$ 6.9
Interest expense									(1.1)	(0.7)	(1.1)
Net loss from equity-method investments									(2.8)	(0.7)	(0.4)
Investment income, net	$ (0.2)	$ 1.7	$ 1.6	$ 1.4	$ 2.0	$ 1.6	$ 1.4	$ 1.4	$ 4.5	$ 6.4	$ 5.4