Quarterly report pursuant to Section 13 or 15(d)

Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details)

v3.22.1
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Feb. 28, 2022
May 31, 2021
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses $ (35.9) $ (4.0)
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (11.7)  
Total, Gross unrealized losses (47.6) (4.0)
Securities in an unrealized loss position for less than twelve months, Fair value 1,116.9 419.9
Securities in an unrealized loss position for more than twelve months, Fair value 207.8  
Total, Fair value 1,324.7 419.9
Asset-Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses (0.3)  
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.2)  
Total, Gross unrealized losses (0.5)  
Securities in an unrealized loss position for less than twelve months, Fair value 15.0 7.1
Securities in an unrealized loss position for more than twelve months, Fair value 5.9  
Total, Fair value 20.9 7.1
Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses (5.1) (0.2)
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.8)  
Total, Gross unrealized losses (5.9) (0.2)
Securities in an unrealized loss position for less than twelve months, Fair value 139.7 22.0
Securities in an unrealized loss position for more than twelve months, Fair value 17.4  
Total, Fair value 157.1 22.0
Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses (28.2) (2.3)
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (4.9)  
Total, Gross unrealized losses (33.1) (2.3)
Securities in an unrealized loss position for less than twelve months, Fair value 778.9 288.2
Securities in an unrealized loss position for more than twelve months, Fair value 88.3  
Total, Fair value 867.2 288.2
U.S. Government Agency Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses (2.3) (1.5)
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (5.8)  
Total, Gross unrealized losses (8.1) (1.5)
Securities in an unrealized loss position for less than twelve months, Fair value 183.3 102.6
Securities in an unrealized loss position for more than twelve months, Fair value 96.2  
Total, Fair value $ 279.5 $ 102.6