Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v2.4.0.8
Fair Value Measurements (Details) (USD $)
In Millions, unless otherwise specified
Aug. 31, 2013
May 31, 2013
Available-for-sale securities:    
Available-for-sale securities $ 3,308.5 $ 3,691.4
Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 11.4  
Available-for-sale securities:    
Available-for-sale securities 3,308.5 3,691.4
Other securities 11.6 10.7
Liabilities:    
Other long-term liabilities 11.6 10.7
Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 3.0  
Money Market Funds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0.1  
General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 6.3  
Available-for-sale securities:    
Available-for-sale securities 1,600.4 1,456.8
Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 131.4 203.9
Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 2.0  
Available-for-sale securities:    
Available-for-sale securities 830.8 754.0
Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 745.9 1,276.7
Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0.1  
Available-for-sale securities:    
Available-for-sale securities 0 0
Other securities 11.6 10.7
Liabilities:    
Other long-term liabilities 11.6 10.7
Quoted prices in active markets (Level 1) [Member] | Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Quoted prices in active markets (Level 1) [Member] | Money Market Funds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0.1  
Quoted prices in active markets (Level 1) [Member] | General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Available-for-sale securities:    
Available-for-sale securities 0 0
Quoted prices in active markets (Level 1) [Member] | Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 0 0
Quoted prices in active markets (Level 1) [Member] | Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Available-for-sale securities:    
Available-for-sale securities 0 0
Quoted prices in active markets (Level 1) [Member] | Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 0 0
Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 11.3  
Available-for-sale securities:    
Available-for-sale securities 3,308.5 3,691.4
Other securities 0 0
Liabilities:    
Other long-term liabilities 0 0
Significant other observable Inputs (Level 2) [Member] | Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 3.0  
Significant other observable Inputs (Level 2) [Member] | Money Market Funds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Significant other observable Inputs (Level 2) [Member] | General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 6.3  
Available-for-sale securities:    
Available-for-sale securities 1,600.4 1,456.8
Significant other observable Inputs (Level 2) [Member] | Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 131.4 203.9
Significant other observable Inputs (Level 2) [Member] | Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 2.0  
Available-for-sale securities:    
Available-for-sale securities 830.8 754.0
Significant other observable Inputs (Level 2) [Member] | Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 745.9 1,276.7
Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Available-for-sale securities:    
Available-for-sale securities 0 0
Other securities 0 0
Liabilities:    
Other long-term liabilities 0 0
Significant unobservable Inputs (Level 3) [Member] | Commercial Paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Significant unobservable Inputs (Level 3) [Member] | Money Market Funds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Significant unobservable Inputs (Level 3) [Member] | General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Available-for-sale securities:    
Available-for-sale securities 0 0
Significant unobservable Inputs (Level 3) [Member] | Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 0 0
Significant unobservable Inputs (Level 3) [Member] | Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Cash equivalents:    
Cash equivalents 0  
Available-for-sale securities:    
Available-for-sale securities 0 0
Significant unobservable Inputs (Level 3) [Member] | Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities $ 0 $ 0