Quarterly report pursuant to Section 13 or 15(d)

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

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Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
$ in Millions
 3 Months Ended 12 Months Ended
Aug. 31, 2024
USD ($)
Item
Segment
Aug. 31, 2023
USD ($)
Item
May 31, 2025
USD ($)
May 31, 2024
USD ($)
Item
Accounting Policies [Line Items]        
Number of reportable segments | Segment 1      
Revision increased net cash provided by investing activities $ 37.2      
Allowance for credit losses 25.0     $ 21.3
Advance collections 1.7     0.7
Maximum individual health insurance claims liability       0.5
Stock-based compensation costs recognized $ 16.5 $ 16.0    
Change in accounting principle, accounting standards update, adopted [true false] false      
Forecast [Member]        
Accounting Policies [Line Items]        
Maximum individual health insurance claims liability     $ 0.5  
Trade Receivables [Member]        
Accounting Policies [Line Items]        
Receivables $ 162.5     141.3
Purchased Receivables [Member]        
Accounting Policies [Line Items]        
Receivables $ 988.7     $ 939.6
Accounts And Unbilled Receivables [Member]        
Accounting Policies [Line Items]        
Number of clients creating a credit concentration | Item 0     0
Revenue [Member]        
Accounting Policies [Line Items]        
Number of clients creating a credit concentration | Item 0 0    
PEO Aggregate Claims Exceeding $1.0M [Member] | Minimum [Member]        
Accounting Policies [Line Items]        
Individual workers' compensation claims liability       $ 1.0
PEO Aggregate Claims Exceeding $1.0M [Member] | Minimum [Member] | Forecast [Member]        
Accounting Policies [Line Items]        
Individual workers' compensation claims liability     1.0  
PEO Aggregate Claims Exceeding $1.0M [Member] | Maximum [Member]        
Accounting Policies [Line Items]        
Maximum individual workers' compensation claims liability       $ 1.0
PEO Aggregate Claims Exceeding $1.0M [Member] | Maximum [Member] | Forecast [Member]        
Accounting Policies [Line Items]        
Maximum individual workers' compensation claims liability     $ 1.0