Annual report pursuant to Section 13 and 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
12 Months Ended
May 31, 2022
May 31, 2021
May 31, 2020
Revenue from Contract with Customer [Abstract]      
Payroll wages and payroll taxes $ 24,070.2 $ 20,587.1 $ 20,463.8
State unemployment insurance (included in payroll wages and payroll taxes) 139.1 119.0 85.7
Guaranteed cost benefit plans $ 641.4 $ 586.4 $ 647.0