Annual report pursuant to Section 13 and 15(d)

Funds Held for Clients and Corporate Investments (Narrative) (Details)

v3.23.2
Funds Held for Clients and Corporate Investments (Narrative) (Details)
$ in Millions
12 Months Ended
May 31, 2023
USD ($)
Security
May 31, 2022
USD ($)
Security
Schedule of Available-for-sale Securities [Line Items]    
Gross unrealized losses on available-for-sale securities $ 179.4 $ 139.0
Net unrealized losses on available-for-sale securities $ 175.3 $ 136.3
Number of available-for-sale securities in an unrealized loss position | Security 967 817
Percentage of available-for-sale securities in an unrealized loss position 88.00% 64.00%
Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross unrealized losses on available-for-sale securities $ 31.1 $ 19.0
Corporate Bonds [Member] | Minimum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Jun. 01, 2023  
Corporate Bonds [Member] | Maximum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Aug. 16, 2029  
Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross unrealized losses on available-for-sale securities $ 105.3 $ 92.5
Municipal Bonds [Member] | Minimum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Aug. 01, 2023  
Municipal Bonds [Member] | Maximum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Dec. 01, 2030  
Variable Rate Demand Notes [Member] | Minimum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities contractual maturities 20 years  
Variable Rate Demand Notes [Member] | Maximum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities contractual maturities 30 years