Quarterly report pursuant to Section 13 or 15(d)

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

v3.19.3.a.u2
Funds Held for Clients and Corporate Investments (Securities in Unrealized Loss Position) (Details) - USD ($)
$ in Millions
Nov. 30, 2019
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 $ (1.5)  
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.4) $ (2.7)
Total, Gross unrealized losses (1.9) (2.7)
Securities in an unrealized loss position for less than twelve months, Fair value 329.2 9.4
Securities in an unrealized loss position for more than twelve months, Fair value 92.1 558.5
Total, Fair value 421.3 567.9
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 (0.1)  
Total, Gross unrealized losses (0.1)  
Securities in an unrealized loss position for less than twelve months, Fair value 25.3  
Total, Fair value 25.3  
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 (0.2)  
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.1) (0.9)
Total, Gross unrealized losses (0.3) (0.9)
Securities in an unrealized loss position for less than twelve months, Fair value 66.2 1.5
Securities in an unrealized loss position for more than twelve months, Fair value 16.2 133.8
Total, Fair value 82.4 135.3
General Obligation Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses   (0.3)
Total, Gross unrealized losses   (0.3)
Securities in an unrealized loss position for less than twelve months, Fair value   3.0
Securities in an unrealized loss position for more than twelve months, Fair value   168.3
Total, Fair value   171.3
Pre-Refunded Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for less than twelve months, Fair value   0.1
Securities in an unrealized loss position for more than twelve months, Fair value   1.6
Total, Fair value   1.7
Revenue Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses   (0.2)
Total, Gross unrealized losses   (0.2)
Securities in an unrealized loss position for less than twelve months, Fair value 5.2 0.1
Securities in an unrealized loss position for more than twelve months, Fair value   79.2
Total, Fair value 5.2 79.3
U.S. Government Agency 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)  
Securities in an unrealized loss position for more than twelve months, Gross unrealized losses (0.3) (1.3)
Total, Gross unrealized losses (1.5) (1.3)
Securities in an unrealized loss position for less than twelve months, Fair value 232.5 4.7
Securities in an unrealized loss position for more than twelve months, Fair value 75.9 175.6
Total, Fair value $ 308.4 $ 180.3