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, 2012
Nov. 30, 2011
Nov. 30, 2012
Nov. 30, 2011
May 31, 2012
Goodwill and Intangible Assets, Net of Accumulated Amortization (Textual)          
Goodwill $ 517.4   $ 517.4   $ 517.4
Amortization expense relating to intangible assets $ 4.7 $ 5.7 $ 9.4 $ 11.4