Annual report pursuant to Section 13 and 15(d)

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

v3.5.0.2
Goodwill and Intangible Assets, Net of Accumulated Amortization (Narrative) (Details) - USD ($)
$ in Millions
 12 Months Ended
May 31, 2016
May 31, 2015
May 31, 2014
Finite-Lived Intangible Assets [Line Items]      
Goodwill $ 657.1 $ 561.5  
Acquired intangible assets with weighted-average amortization periods 9 years 6 months    
Amortization expense $ 15.9 $ 14.5 $ 15.9
Client Lists [Member]      
Finite-Lived Intangible Assets [Line Items]      
Acquired intangible assets with weighted-average amortization periods 9 years 8 months 12 days    
Other Intangible Assets [Member]      
Finite-Lived Intangible Assets [Line Items]      
Acquired intangible assets with weighted-average amortization periods 5 years    
Advance Partners [Member]      
Finite-Lived Intangible Assets [Line Items]      
Goodwill acquired $ 95.6