Quarterly report pursuant to Section 13 or 15(d)

Service Revenue (Summary of PEO Pass-Through Costs Netted in Revenue) (Details)

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Service Revenue (Summary of PEO Pass-Through Costs Netted in Revenue) (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Nov. 30, 2023
Nov. 30, 2022
Nov. 30, 2023
Nov. 30, 2022
Revenue from Contract with Customer [Abstract]        
Payroll wages and payroll taxes $ 6,646.9 $ 6,333.3 $ 13,061.5 $ 12,671.1
State unemployment insurance (included in payroll wages and payroll taxes) 19.7 30.3 38.3 39.8
Guaranteed cost benefit plans $ 171.3 $ 180.3 $ 333.8 $ 337.0