Quarterly report pursuant to Section 13 or 15(d)

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

v3.23.1
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Feb. 28, 2023
May 31, 2022
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses $ (73.7) $ (116.2)
Securities in an unrealized loss position for less than twelve months, Fair value 2,012.5 2,059.6
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (157.6) (22.8)
Securities in an unrealized loss position for more than twelve months, Fair value 1,159.8 200.7
Total, Gross unrealized losses (231.3) (139.0)
Total, Fair value 3,172.3 2,260.3
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 (0.6) (0.9)
Securities in an unrealized loss position for less than twelve months, Fair value 68.6 48.5
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (1.5) (0.3)
Securities in an unrealized loss position for more than twelve months, Fair value 19.9 5.7
Total, Gross unrealized losses (2.1) (1.2)
Total, Fair value 88.5 54.2
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 (29.4) (17.5)
Securities in an unrealized loss position for less than twelve months, Fair value 1,072.9 425.4
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (18.5) (1.5)
Securities in an unrealized loss position for more than twelve months, Fair value 142.4 16.7
Total, Gross unrealized losses (47.9) (19.0)
Total, Fair value 1,215.3 442.1
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 (23.3) (81.9)
Securities in an unrealized loss position for less than twelve months, Fair value 555.3 1,171.5
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (106.0) (10.6)
Securities in an unrealized loss position for more than twelve months, Fair value 743.2 86.6
Total, Gross unrealized losses (129.3) (92.5)
Total, Fair value 1,298.5 1,258.1
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 (20.4) (15.9)
Securities in an unrealized loss position for less than twelve months, Fair value 315.7 414.2
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (31.6) (10.4)
Securities in an unrealized loss position for more than twelve months, Fair value 254.3 91.7
Total, Gross unrealized losses (52.0) (26.3)
Total, Fair value $ 570.0 $ 505.9