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, unless otherwise specified
3 Months Ended 6 Months Ended
Nov. 30, 2014
Nov. 30, 2013
Nov. 30, 2014
Nov. 30, 2013
May 31, 2014
Goodwill and Intangible Assets, Net of Accumulated Amortization (Textual)          
Goodwill $ 563.8us-gaap_Goodwill   $ 563.8us-gaap_Goodwill   $ 540.3us-gaap_Goodwill
Amortization expense relating to intangible assets $ 3.5us-gaap_AmortizationOfIntangibleAssets $ 3.8us-gaap_AmortizationOfIntangibleAssets $ 7.3us-gaap_AmortizationOfIntangibleAssets $ 7.5us-gaap_AmortizationOfIntangibleAssets