Quarterly report pursuant to Section 13 or 15(d)

Funds Held for Clients and Corporate Investments (Narrative) (Details)

v3.21.2
Funds Held for Clients and Corporate Investments (Narrative) (Details)
$ in Millions
 3 Months Ended
Aug. 31, 2021
USD ($)
security
May 31, 2021
USD ($)
security
Schedule of Available-for-sale Securities [Line Items]    
Net unrealized gains on available-for-sale securities $ 78.7 $ 79.3
Number of available-for-sale securities in an unrealized loss position | security 107 137
Percentage of available-for-sale securities in an unrealized loss position 9.00% 11.00%
Gross unrealized losses on available-for-sale securities $ 1.8 $ 4.0
Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross unrealized losses on available-for-sale securities $ 0.2 0.2
Corporate Bonds [Member] | Minimum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Sep. 07, 2021  
Corporate Bonds [Member] | Maximum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Aug. 12, 2028  
Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Gross unrealized losses on available-for-sale securities $ 0.7 $ 2.3
Municipal Bonds [Member] | Minimum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Sep. 01, 2021  
Municipal Bonds [Member] | Maximum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities maturity date Nov. 15, 2028  
VRDNs [Member] | Minimum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities contractual maturities 20 years  
VRDNs [Member] | Maximum [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities contractual maturities 30 years