Annual report pursuant to Section 13 and 15(d)

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

v3.2.0.727
Goodwill and Intangible Assets, Net of Accumulated Amortization (Details Textual) - USD ($)
$ in Millions
 12 Months Ended
May. 31, 2015
May. 31, 2014
May. 31, 2013
Goodwill and Intangible Assets, Net of Accumulated Amortization (Textual)      
Goodwill $ 561.5 $ 540.3  
Amortization expense relating to intangible assets $ 14.5 $ 15.9 $ 19.0
Finite-Lived Intangible Assets [Line Items]      
Acquired intangible assets, Weighted average amortization period 7 years 7 months 6 days    
Customer Lists [Member]      
Finite-Lived Intangible Assets [Line Items]      
Acquired intangible assets, Weighted average amortization period 8 years    
Other Intangible Assets [Member]      
Finite-Lived Intangible Assets [Line Items]      
Acquired intangible assets, Weighted average amortization period 3 years