Quarterly report [Sections 13 or 15(d)]

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

v3.26.1
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Feb. 28, 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 $ (3.5) $ (3.0)
Securities in an unrealized loss position for less than twelve months, Fair value 364.1 300.1
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (27.9) (65.0)
Securities in an unrealized loss position for more than twelve months, Fair value 1,258.8 1,651.4
Total, Gross unrealized losses (31.4) (68.0)
Total, Fair value 1,622.9 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   0.0
Securities in an unrealized loss position for less than twelve months, Fair value   16.4
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses   0.0
Securities in an unrealized loss position for more than twelve months, Fair value   2.8
Total, Gross unrealized losses   0.0
Total, Fair value   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 (0.5) (0.1)
Securities in an unrealized loss position for less than twelve months, Fair value 157.6 83.2
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (2.6) (6.9)
Securities in an unrealized loss position for more than twelve months, Fair value 143.7 236.7
Total, Gross unrealized losses (3.1) (7.0)
Total, Fair value 301.3 319.9
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 (1.8) (2.2)
Securities in an unrealized loss position for less than twelve months, Fair value 45.1 48.5
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (18.9) (42.1)
Securities in an unrealized loss position for more than twelve months, Fair value 740.6 880.1
Total, Gross unrealized losses (20.7) (44.3)
Total, Fair value 785.7 928.6
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 (1.2) (0.7)
Securities in an unrealized loss position for less than twelve months, Fair value 161.4 152.0
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 374.5 531.8
Total, Gross unrealized losses (7.6) (16.7)
Total, Fair value $ 535.9 $ 683.8