Annual report pursuant to Section 13 and 15(d)

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

v3.20.2
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
May 31, 2020
May 31, 2019
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Gross unrealized losses $ (1.7)  
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses   $ (2.7)
Total, Gross unrealized losses (1.7) (2.7)
Securities in an unrealized loss position for less than twelve months, Fair value 66.8 9.4
Securities in an unrealized loss position for more than twelve months, Fair value   558.5
Total, Fair value 66.8 567.9
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 (0.1)  
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses   (0.9)
Total, Gross unrealized losses (0.1) (0.9)
Securities in an unrealized loss position for less than twelve months, Fair value 6.5 1.5
Securities in an unrealized loss position for more than twelve months, Fair value   133.8
Total, Fair value 6.5 135.3
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 (1.6)  
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses   (0.5)
Total, Gross unrealized losses (1.6) (0.5)
Securities in an unrealized loss position for less than twelve months, Fair value 60.3 3.2
Securities in an unrealized loss position for more than twelve months, Fair value   249.1
Total, Fair value $ 60.3 252.3
U.S. Government Agency And Treasury Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses   (1.3)
Total, Gross unrealized losses   (1.3)
Securities in an unrealized loss position for less than twelve months, Fair value   4.7
Securities in an unrealized loss position for more than twelve months, Fair value   175.6
Total, Fair value   $ 180.3