Quarterly report pursuant to Section 13 or 15(d)

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

v3.24.1
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Feb. 29, 2024
May 31, 2023
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses $ (21.6) $ (15.2)
Securities in an unrealized loss position for less than twelve months, Fair value 1,203.9 992.5
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (142.8) (164.2)
Securities in an unrealized loss position for more than twelve months, Fair value 1,904.7 1,752.9
Total, Gross unrealized losses (164.4) (179.4)
Total, Fair value 3,108.6 2,745.4
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) (0.1)
Securities in an unrealized loss position for less than twelve months, Fair value 63.2 54.2
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.6) (1.3)
Securities in an unrealized loss position for more than twelve months, Fair value 15.3 23.3
Total, Gross unrealized losses (0.9) (1.4)
Total, Fair value 78.5 77.5
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 (9.5) (5.9)
Securities in an unrealized loss position for less than twelve months, Fair value 792.2 652.0
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (21.7) (25.2)
Securities in an unrealized loss position for more than twelve months, Fair value 478.5 382.7
Total, Gross unrealized losses (31.2) (31.1)
Total, Fair value 1,270.7 1,034.7
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 (7.9) (5.9)
Securities in an unrealized loss position for less than twelve months, Fair value 98.7 86.7
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (83.6) (99.4)
Securities in an unrealized loss position for more than twelve months, Fair value 892.1 889.0
Total, Gross unrealized losses (91.5) (105.3)
Total, Fair value 990.8 975.7
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 (3.9) (3.3)
Securities in an unrealized loss position for less than twelve months, Fair value 249.8 199.6
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (36.9) (38.3)
Securities in an unrealized loss position for more than twelve months, Fair value 518.8 457.9
Total, Gross unrealized losses (40.8) (41.6)
Total, Fair value $ 768.6 $ 657.5