Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.4
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Nov. 30, 2021
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 $ (14.5) $ (4.0)
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.1)  
Total, Gross unrealized losses (14.6) (4.0)
Securities in an unrealized loss position for less than twelve months, Fair value 980.5 419.9
Securities in an unrealized loss position for more than twelve months, Fair value 6.1  
Total, Fair value 986.6 419.9
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 (0.2)  
Total, Gross unrealized losses (0.2)  
Securities in an unrealized loss position for less than twelve months, Fair value 15.2 7.1
Total, Fair value 15.2 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 (1.6) (0.2)
Total, Gross unrealized losses (1.6) (0.2)
Securities in an unrealized loss position for less than twelve months, Fair value 107.0 22.0
Total, Fair value 107.0 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 (9.5) (2.3)
Total, Gross unrealized losses (9.5) (2.3)
Securities in an unrealized loss position for less than twelve months, Fair value 737.1 288.2
Total, Fair value 737.1 288.2
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 (3.2) (1.5)
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.1)  
Total, Gross unrealized losses (3.3) (1.5)
Securities in an unrealized loss position for less than twelve months, Fair value 121.2 102.6
Securities in an unrealized loss position for more than twelve months, Fair value 6.1  
Total, Fair value $ 127.3 $ 102.6