Quarterly report [Sections 13 or 15(d)]

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

v3.25.2
Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
$ in Millions
 3 Months Ended 12 Months Ended
Aug. 31, 2025
USD ($)
Item
Segment
Aug. 31, 2024
USD ($)
Item
May 31, 2026
USD ($)
May 31, 2025
USD ($)
Item
Accounting Policies [Line Items]        
Number of reportable segments | Segment 1      
Allowance for credit losses $ 24.4     $ 26.0
Receivables 1,383.7     1,356.5
Advance collections 2.8     1.8
Maximum individual health insurance claims liability       0.5
Stock-based compensation costs recognized $ 26.8 $ 16.5    
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 $ 222.1     205.4
Purchased Receivables [Member]        
Accounting Policies [Line Items]        
Receivables $ 1,161.6     $ 1,151.1
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]        
Maximum individual workers' compensation claims liability       $ 1.0
Individual workers' compensation claims liability       1.0
PEO Aggregate Claims Exceeding $1.0M [Member] | Minimum [Member] | Forecast [Member]        
Accounting Policies [Line Items]        
Maximum individual workers' compensation claims liability     1.0  
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