Quarterly report pursuant to Section 13 or 15(d)

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

v3.23.4
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Nov. 30, 2023
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 $ (23.1) $ (15.2)
Securities in an unrealized loss position for less than twelve months, Fair value 1,218.6 992.5
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (166.1) (164.2)
Securities in an unrealized loss position for more than twelve months, Fair value 1,936.3 1,752.9
Total, Gross unrealized losses (189.2) (179.4)
Total, Fair value 3,154.9 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 (0.5) (0.1)
Securities in an unrealized loss position for less than twelve months, Fair value 63.0 54.2
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.9) (1.3)
Securities in an unrealized loss position for more than twelve months, Fair value 18.2 23.3
Total, Gross unrealized losses (1.4) (1.4)
Total, Fair value 81.2 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 (12.3) (5.9)
Securities in an unrealized loss position for less than twelve months, Fair value 836.9 652.0
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (25.2) (25.2)
Securities in an unrealized loss position for more than twelve months, Fair value 477.1 382.7
Total, Gross unrealized losses (37.5) (31.1)
Total, Fair value 1,314.0 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 (4.8) (5.9)
Securities in an unrealized loss position for less than twelve months, Fair value 71.2 86.7
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (100.2) (99.4)
Securities in an unrealized loss position for more than twelve months, Fair value 920.3 889.0
Total, Gross unrealized losses (105.0) (105.3)
Total, Fair value 991.5 975.7
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 (5.5) (3.3)
Securities in an unrealized loss position for less than twelve months, Fair value 247.5 199.6
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (39.8) (38.3)
Securities in an unrealized loss position for more than twelve months, Fair value 520.7 457.9
Total, Gross unrealized losses (45.3) (41.6)
Total, Fair value $ 768.2 $ 657.5