Quarterly report pursuant to Section 13 or 15(d)

Funds Held for Clients and Corporate Investments (Details 2)

v3.3.1.900
Funds Held for Clients and Corporate Investments (Details 2)
$ in Millions
 3 Months Ended 6 Months Ended
Nov. 30, 2015
USD ($)
Security
Nov. 30, 2014
USD ($)
Nov. 30, 2015
USD ($)
Security
Nov. 30, 2014
USD ($)
May. 31, 2015
USD ($)
Security
Maturity Date:          
Due in one year or less, Amortized cost $ 348.0   $ 348.0    
Due in one year or less, Fair value 350.5   350.5    
Due after one year through three years, Amortized cost 720.4   720.4    
Due after one year through three years, Fair value 726.8   726.8    
Due after three years through five years, Amortized cost 877.7   877.7    
Due after three years through five years, Fair value 888.1   888.1    
Due after five years, Amortized cost 937.3   937.3    
Due after five years, Fair value 951.9   951.9    
Total, Amortized cost 2,883.4   2,883.4    
Fair value 2,917.3   2,917.3   $ 3,595.6
Funds Held for Clients and Corporate Investments (Textual)          
Net unrealized gain on available-for-sale securities $ 33.9   $ 33.9   $ 13.6
Number of available-for-sale securities in an unrealized loss position | Security 93   93   280
Gross realized gains $ 0.0 $ 0.1 $ 0.0 $ 0.2  
Gross realized losses $ 0.0 $ 0.0 $ 0.0 $ 0.0  
Minimum maturity period for VRDNs primarily categorized as due after five years (in years)     20 years    
Maximum maturity period for VRDNs, primarily categorized as due after five years (in years)     30 years