Annual report pursuant to Section 13 and 15(d)

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

v3.10.0.1
Goodwill and Intangible Assets, Net of Accumulated Amortization (Narrative) (Details) - USD ($)
$ in Millions
 12 Months Ended
May 31, 2018
May 31, 2017
May 31, 2016
Goodwill and Intangible Assets [Line Items]      
Goodwill $ 814.0 $ 657.1  
Acquired intangible assets with weighted-average amortization periods 8 years 9 months 18 days    
Amortization expense $ 21.1 $ 18.1 $ 15.9
Client Lists [Member]      
Goodwill and Intangible Assets [Line Items]      
Acquired intangible assets with weighted-average amortization periods 8 years 9 months 18 days    
Other Intangible Assets [Member]      
Goodwill and Intangible Assets [Line Items]      
Acquired intangible assets with weighted-average amortization periods 3 years    
HROI And Lessor [Member]      
Goodwill and Intangible Assets [Line Items]      
Increased in goodwill result of acquisitions $ 156.9