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 9 Months Ended
Feb. 29, 2012
Feb. 28, 2011
Feb. 29, 2012
Feb. 28, 2011
May 31, 2011
Goodwill and Intangible Assets, Net of Accumulated Amortization (Textual) [Abstract]          
Goodwill $ 518.1   $ 518.1   $ 513.7
Amortization expense $ 5.8 $ 5.4 $ 17.2 $ 14.7