Quarterly report pursuant to Section 13 or 15(d)

Goodwill and Intangible Assets, Net of Accumulated Amortization (Details Textual)

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Goodwill and Intangible Assets, Net of Accumulated Amortization (Details Textual) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Nov. 30, 2015
Nov. 30, 2014
Nov. 30, 2015
Nov. 30, 2014
May. 31, 2015
Goodwill and Intangible Assets, Net of Accumulated Amortization (Textual)          
Goodwill $ 561.5   $ 561.5   $ 561.5
Amortization expense relating to intangible assets $ 3.0 $ 3.5 $ 6.0 $ 7.3