Quarterly report [Sections 13 or 15(d)]

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

v3.25.1
Description of Business, Basis of Presentation, and Significant Accounting Policies (Narrative) (Details)
$ in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Feb. 28, 2025
USD ($)
Item
Feb. 29, 2024
USD ($)
Item
Feb. 28, 2025
USD ($)
Item
Segment
Feb. 29, 2024
USD ($)
Item
May 31, 2025
USD ($)
May 31, 2024
USD ($)
Item
Accounting Policies [Line Items]            
Number of reportable segments | Segment     1      
Allowance for credit losses $ 23.8   $ 23.8     $ 21.3
Advance collections 0.6   0.6     0.7
Maximum individual health insurance claims liability           0.5
Stock-based compensation costs recognized $ 17.6 $ 14.4 $ 50.5 $ 45.1    
Change in accounting principle, accounting standards update, adopted [true false] false   false      
Forecast [Member]            
Accounting Policies [Line Items]            
Maximum individual health insurance claims liability         $ 0.5  
Trade Receivables [Member]            
Accounting Policies [Line Items]            
Receivables $ 170.5   $ 170.5     141.3
Purchased Receivables [Member]            
Accounting Policies [Line Items]            
Receivables $ 1,100.0   $ 1,100.0     $ 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 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