Quarterly report pursuant to Section 13 or 15(d)

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

v3.23.1
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, 2023
USD ($)
Item
Feb. 28, 2022
USD ($)
Item
Feb. 28, 2023
USD ($)
Item
Segment
Feb. 28, 2022
USD ($)
Item
May 31, 2023
USD ($)
May 31, 2022
USD ($)
Item
Accounting Policies [Line Items]            
Number of reportable segments | Segment     1      
Allowance for credit losses $ 21.1   $ 21.1     $ 18.2
Advance collections 3.9   3.9     2.6
Maximum individual health insurance claims liability           0.5
Stock-based compensation costs recognized $ 16.3 $ 12.8 $ 46.0 $ 39.2    
Accounting Standards Update 2021-10 [Member]            
Accounting Policies [Line Items]            
Change in accounting principle, accounting standards update, adoption date Jun. 01, 2022   Jun. 01, 2022      
Change in accounting principle, accounting standards update, adopted [true false] true   true      
Change in accounting principle, accounting standards update, immaterial effect [true false] true   true      
Forecast [Member]            
Accounting Policies [Line Items]            
Maximum individual health insurance claims liability         $ 0.5  
Trade Receivables [Member]            
Accounting Policies [Line Items]            
Receivables $ 238.5   $ 238.5     123.2
Purchased Receivables [Member]            
Accounting Policies [Line Items]            
Receivables $ 582.0   $ 582.0     $ 618.8
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 [Member]            
Accounting Policies [Line Items]            
Individual workers' compensation claims liability           $ 1.0
PEO [Member] | Forecast [Member]            
Accounting Policies [Line Items]            
Individual workers' compensation claims liability         1.0  
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           $ 2.0
PEO Aggregate Claims Exceeding $1.0M [Member] | Maximum [Member] | Forecast [Member]            
Accounting Policies [Line Items]            
Maximum individual workers' compensation claims liability         $ 2.0