Quarterly report pursuant to Section 13 or 15(d)

Funds Held for Clients and Corporate Investments (Details 2)

v2.4.0.6
Funds Held for Clients and Corporate Investments (Details 2) (USD $)
 3 Months Ended 6 Months Ended
Nov. 30, 2012
Security
Nov. 30, 2011
Nov. 30, 2012
Security
Nov. 30, 2011
May 31, 2012
Security
Maturity Date:          
Due in one year or less, Amortized cost $ 299,200,000   $ 299,200,000    
Due in one year or less, Fair value 302,800,000   302,800,000    
Due after one year through three years, Amortized cost 705,100,000   705,100,000    
Due after one year through three years, Fair value 724,900,000   724,900,000    
Due after three years through five years, Amortized cost 643,500,000   643,500,000    
Due after three years through five years, Fair value 666,500,000   666,500,000    
Due after five years, Amortized cost 1,297,200,000   1,297,200,000    
Due after five years, Fair value 1,313,700,000   1,313,700,000    
Total, Amortized cost 2,945,000,000   2,945,000,000    
Total, Fair value 3,007,900,000   3,007,900,000   3,059,000,000
Funds Held for Clients and Corporate Investments (Textual)          
Net unrealized gain on available-for-sale securities 62,900,000   62,900,000   59,500,000
Number of available-for-sale securities in an unrealized loss position 20   20   35
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses 100,000   100,000   300,000
Gross realized gains 100,000 100,000 300,000 200,000  
Gross realized losses 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        
Separately Designated Demand Deposit Account $ 19,600,000   $ 19,600,000   $ 13,700,000