Annual report pursuant to Section 13 and 15(d)

Investment Income, Net (Details)

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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