Annual report pursuant to Section 13 and 15(d)

Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)

v3.20.2
Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
$ / shares in Units, $ in Millions
 12 Months Ended
Jul. 09, 2020
$ / shares
Jun. 01, 2019
USD ($)
May 31, 2020
USD ($)
segment
May 31, 2019
USD ($)
May 31, 2018
USD ($)
Dec. 20, 2018
USD ($)
Aug. 18, 2017
USD ($)
Accounting Policies [Line Items]              
Number of reportable segments | segment     1        
Cash and cash equivalents     $ 905.2 $ 673.6 $ 358.2    
Allowance for doubtful accounts     12.5 7.5      
Advance collections     6.1 4.2      
Goodwill     1,791.1 1,782.6 814.0    
Goodwill, impairment loss     0.0 0.0 0.0    
Impairment of long-lived assets     0.0 0.0 0.0    
Realized gains or losses from foreign exchange transactions     0.0 0.0 $ 0.0    
Impairment loss, assets recognized from the costs to obtain and fufill contracts     0.0 0.0      
Workers' compensation insurance costs in current liabilities     72.3 71.1      
Workers' compensation insurance costs in long-term liabilities     101.3 99.2      
Maximum individual health insurance claims liability     0.3 0.3      
PEO accrued health insurance and dental and vision plan reserves in current liabilities     36.7 25.4      
Reserve for uncertain tax positions     26.5 21.6      
Operating lease, right-of-use asset     114.8        
Operating lease, liability     134.1        
Subsequent Event [Member]              
Accounting Policies [Line Items]              
Declared date Jul. 09, 2020            
Quarterly dividend per share | $ / shares $ 0.62            
Payable date Aug. 27, 2020            
Record date Aug. 03, 2020            
ASU 2016-02 [Member]              
Accounting Policies [Line Items]              
Increase in lease-related assets and liabilities   $ 116.4          
Operating lease, right-of-use asset   116.4          
Operating lease, liability   135.3          
Unamortized landlord allowances and lease incentives   $ 18.9          
Trade Receivables [Member]              
Accounting Policies [Line Items]              
Receivables     84.7 94.5      
Purchased Receivables [Member]              
Accounting Policies [Line Items]              
Receivables     $ 311.9 $ 333.5      
Minimum [Member]              
Accounting Policies [Line Items]              
Payroll funding fees average collection period     35 days        
Minimum [Member] | Finite Lived Assets [Member]              
Accounting Policies [Line Items]              
Amortization period     3 years        
Minimum [Member] | Software [Member]              
Accounting Policies [Line Items]              
Estimated useful lives     3 years        
Minimum [Member] | Software Development [Member]              
Accounting Policies [Line Items]              
Estimated useful lives     12 years        
Maximum [Member]              
Accounting Policies [Line Items]              
Payroll funding fees average collection period     45 days        
Maximum [Member] | Finite Lived Assets [Member]              
Accounting Policies [Line Items]              
Amortization period     12 years        
Maximum [Member] | Software [Member]              
Accounting Policies [Line Items]              
Estimated useful lives     5 years        
Oasis Outsourcing Group Holdings, L.P. [Member]              
Accounting Policies [Line Items]              
Goodwill           $ 976.6  
HR Outsourcing Holdings, Inc. [Member]              
Accounting Policies [Line Items]              
Goodwill             $ 51.1
Europe [Member] | Revenue [Member] | Geographic Concentration Risk [Member]              
Accounting Policies [Line Items]              
Total percentage     1.00% 1.00%      
Europe [Member] | Revenue [Member] | Geographic Concentration Risk [Member] | Maximum [Member]              
Accounting Policies [Line Items]              
Total percentage         1.00%    
Europe [Member] | Long Lived Assets [Member] | Geographic Concentration Risk [Member]              
Accounting Policies [Line Items]              
Total percentage     5.00% 5.00%      
PEO And Insurance Solutions [Member]              
Accounting Policies [Line Items]              
Cash and cash equivalents     $ 136.4 $ 178.8      
PEO [Member]              
Accounting Policies [Line Items]              
Maximum individual workers' compensation claims liability     $ 1.0        
PEO [Member] | Minimum [Member]              
Accounting Policies [Line Items]              
Maximum individual workers' compensation claims liability       0.5      
PEO [Member] | Maximum [Member]              
Accounting Policies [Line Items]              
Maximum individual workers' compensation claims liability       $ 1.0