Annual report pursuant to Section 13 and 15(d)

Funds Held for Clients and Corporate Investments (Details 2)

v2.4.0.8
Funds Held for Clients and Corporate Investments (Details 2) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 12 Months Ended
May 31, 2013
Security
Feb. 28, 2013
Nov. 30, 2012
Aug. 31, 2012
May 31, 2012
Security
Feb. 29, 2012
Nov. 30, 2011
Aug. 31, 2011
May 31, 2013
Security
May 31, 2012
Security
May 31, 2011
Funds Held for Clients and Corporate Investments [Abstract]                      
Gross realized gains                 $ 0.9 $ 1.0 $ 1.3
Gross realized losses                 0 0 0
Net realized gains 0 0.6 0.1 0.2 0.4 0.4 0.1 0.1 0.9 1.0 1.3
Maturity Date:                      
Due in one year or less, Amortized cost 274.3               274.3    
Due in one year or less, Fair value 276.2               276.2    
Due after one year through three years, Amortized cost 701.2               701.2    
Due after one year through three years, Fair value 718.6               718.6    
Due after three years through five years, Amortized cost 693.4               693.4    
Due after three years through five years, Fair value 709.7               709.7    
Due after five years, Amortized cost 1,987.8               1,987.8    
Due after five years, Fair value 1,986.9               1,986.9    
Total, Amortized cost 3,656.7               3,656.7    
Fair value 3,691.4       3,059.0       3,691.4 3,059.0  
Funds Held for Clients and Corporate Investments (Textual)                      
Separately designated demand deposit account 23.4       13.7       23.4 13.7  
Net unrealized gain on available-for-sale securities 34.7       59.5       34.7 59.5  
Number of available-for-sale securities in an unrealized loss position 147       35       147 35  
Total, Gross unrealized losses $ 5.7       $ 0.3       $ 5.7 $ 0.3  
Minimum maturity period for VRDNs primarily categorized as due after five years (in years) 20 years               20 years    
Maximum maturity period for VRDNs, primarily categorized as due after five years (in years) 30 years               30 years