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 6 Months Ended
Nov. 30, 2017
Nov. 30, 2016
Nov. 30, 2017
Nov. 30, 2016
Interest income on corporate funds $ 2.7 $ 2.4 $ 5.6 $ 4.8
Interest expense (1.3) (0.6) (2.1) (1.3)
Net gain/(loss) from equity-method investments 0.3 (0.9) 0.3 (1.1)
Investment income, net $ 1.7 $ 0.9 $ 3.8 $ 2.4