Quarterly report pursuant to Section 13 or 15(d)

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

v3.21.1
Funds Held for Clients and Corporate Investments (Funds Held for Clients and Corporate Investments) (Details) - USD ($)
$ in Millions
Feb. 28, 2021
May 31, 2020
Schedule of Available-for-sale Securities [Line Items]    
Funds held for clients' money market securities and other restricted cash equivalents, Amortized cost $ 1,184.9 $ 683.5
Funds held for clients' money market securities and other restricted cash equivalents, Fair value 1,184.9 683.5
Available-for-sale securities, Amortized cost 3,125.3 2,657.2
Available-for-sale securities, Gross unrealized gains 86.5 101.7
Available-for-sale securities, Gross unrealized losses (4.4) (1.7)
Available-for-sale securities, Fair value 3,207.4 2,757.2
Other, Amortized cost 26.3 25.4
Other, Gross unrealized gains 6.3 2.2
Other, Gross unrealized losses   (0.4)
Other, Fair value 32.6 27.2
Total funds held for clients and corporate investments, Amortized cost 4,336.5 3,366.1
Total funds held for clients and corporate investments, Gross unrealized gains 92.8 103.9
Total funds held for clients and corporate investments, Gross unrealized losses (4.4) (2.1)
Total funds held for clients and corporate investments, Fair value 4,424.9 3,467.9
Asset-Backed Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 82.3 68.0
Available-for-sale securities, Gross unrealized gains 1.6 1.7
Available-for-sale securities, Fair value 83.9 69.7
Corporate Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 626.4 649.6
Available-for-sale securities, Gross unrealized gains 30.4 34.1
Available-for-sale securities, Gross unrealized losses (0.2) (0.1)
Available-for-sale securities, Fair value 656.6 683.6
Municipal Bonds [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 1,699.3 1,373.8
Available-for-sale securities, Gross unrealized gains 33.9 37.4
Available-for-sale securities, Gross unrealized losses (2.9) (1.6)
Available-for-sale securities, Fair value 1,730.3 1,409.6
U.S. Government Agency And Treasury Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 546.2 565.8
Available-for-sale securities, Gross unrealized gains 20.6 28.5
Available-for-sale securities, Gross unrealized losses (1.3)  
Available-for-sale securities, Fair value 565.5 $ 594.3
VRDNs [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale securities, Amortized cost 171.1  
Available-for-sale securities, Fair value $ 171.1