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 9 Months Ended
Feb. 28, 2018
Feb. 28, 2017
Feb. 28, 2018
Feb. 28, 2017
Investment Income, Net [Abstract]        
Interest income on corporate funds $ 3.1 $ 2.4 $ 8.7 $ 7.2
Interest expense (1.1) (0.6) (3.2) (1.9)
Net gain/(loss) from equity-method investments 0.3 (0.6) 0.6 (1.7)
Investment income, net $ 2.3 $ 1.2 $ 6.1 $ 3.6