v3.26.1
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
May 31, 2026
May 31, 2025
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses $ (31.5) $ (3.0)
Securities in an unrealized loss position for less than twelve months, Fair value 1,850.2 300.1
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (28.3) (65.0)
Securities in an unrealized loss position for more than twelve months, Fair value 1,178.5 1,651.4
Total, Gross unrealized losses (59.8) (68.0)
Total, Fair value 3,028.7 1,951.5
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 (0.1) 0.0
Securities in an unrealized loss position for less than twelve months, Fair value 21.7 16.4
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses 0.0 0.0
Securities in an unrealized loss position for more than twelve months, Fair value 0.0 2.8
Total, Gross unrealized losses (0.1) 0.0
Total, Fair value 21.7 19.2
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 (16.3) (0.1)
Securities in an unrealized loss position for less than twelve months, Fair value 1,148.8 83.2
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (2.5) (6.9)
Securities in an unrealized loss position for more than twelve months, Fair value 128.0 236.7
Total, Gross unrealized losses (18.8) (7.0)
Total, Fair value 1,276.8 319.9
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 (1.7) (2.2)
Securities in an unrealized loss position for less than twelve months, Fair value 69.0 48.5
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (19.4) (42.1)
Securities in an unrealized loss position for more than twelve months, Fair value 713.2 880.1
Total, Gross unrealized losses (21.1) (44.3)
Total, Fair value 782.2 928.6
U.S. Government Agency And Treasury Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses (13.4) (0.7)
Securities in an unrealized loss position for less than twelve months, Fair value 610.7 152.0
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (6.4) (16.0)
Securities in an unrealized loss position for more than twelve months, Fair value 337.3 531.8
Total, Gross unrealized losses (19.8) (16.7)
Total, Fair value $ 948.0 $ 683.8