Quarterly report pursuant to Section 13 or 15(d)

Investment Income, Net (Schedule of Investment Income, Net) (Details)

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Investment Income, Net (Schedule of Investment Income, Net) (Details) - USD ($)
$ in Millions
3 Months Ended
Aug. 31, 2017
Aug. 31, 2016
Investment Income, Net [Abstract]    
Interest income on corporate funds $ 2.9 $ 2.4
Interest expense (0.8) (0.7)
Net loss from equity-method investments   (0.2)
Investment income, net $ 2.1 $ 1.5