Annual report pursuant to Section 13 and 15(d)

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

v3.19.2
Goodwill and Intangible Assets, Net of Accumulated Amortization (Narrative) (Details) - USD ($)
$ in Millions
 12 Months Ended
May 31, 2019
May 31, 2018
May 31, 2017
Dec. 20, 2018
Goodwill and Intangible Assets [Line Items]        
Goodwill $ 1,782.6 $ 814.0 [1] $ 657.1  
Acquired intangible assets with weighted-average amortization periods 9 years 8 months 12 days      
Amortization expense $ 55.8 $ 21.1 $ 18.1  
Client Lists [Member]        
Goodwill and Intangible Assets [Line Items]        
Acquired intangible assets with weighted-average amortization periods 10 years      
Other Intangible Assets [Member]        
Goodwill and Intangible Assets [Line Items]        
Acquired intangible assets with weighted-average amortization periods 3 years      
Oasis Outsourcing Group Holdings, L.P. [Member]        
Goodwill and Intangible Assets [Line Items]        
Goodwill       $ 972.1
[1] Amounts have been adjusted to reflect the adoption of ASC Topic 606 and to provide further detail related to certain professional employer organization ("PEO") balances.