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
Feb. 28, 2014
May 31, 2013
Available-for-sale securities:    
Available-for-sale securities $ 3,089.5 $ 3,691.4
Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 291.2  
Available-for-sale securities:    
Available-for-sale securities 3,089.5 3,691.4
Other securities 12.1 10.7
Liabilities:    
Other long-term liabilities 12.1 10.7
General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 5.2  
Available-for-sale securities:    
Available-for-sale securities 1,649.5 1,456.8
Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 4.0  
Available-for-sale securities:    
Available-for-sale securities 126.2 203.9
Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 9.6  
Available-for-sale securities:    
Available-for-sale securities 848.3 754.0
Commercial paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 272.3  
Money market securities [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 0.1  
Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
   
Available-for-sale securities:    
Available-for-sale securities 465.5 1,276.7
Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 0.1  
Available-for-sale securities:    
Available-for-sale securities 0 0
Other securities 12.1 10.7
Liabilities:    
Other long-term liabilities 12.1 10.7
Quoted prices in active markets (Level 1) [Member] | General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
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]
   
Assets:    
Cash Equivalents 0  
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]
   
Assets:    
Cash Equivalents 0  
Available-for-sale securities:    
Available-for-sale securities 0 0
Quoted prices in active markets (Level 1) [Member] | Commercial paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 0  
Quoted prices in active markets (Level 1) [Member] | Money market securities [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 0.1  
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]
   
Assets:    
Cash Equivalents 291.1  
Available-for-sale securities:    
Available-for-sale securities 3,089.5 3,691.4
Other securities 0 0
Liabilities:    
Other long-term liabilities 0 0
Significant other observable Inputs (Level 2) [Member] | General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 5.2  
Available-for-sale securities:    
Available-for-sale securities 1,649.5 1,456.8
Significant other observable Inputs (Level 2) [Member] | Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 4.0  
Available-for-sale securities:    
Available-for-sale securities 126.2 203.9
Significant other observable Inputs (Level 2) [Member] | Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 9.6  
Available-for-sale securities:    
Available-for-sale securities 848.3 754.0
Significant other observable Inputs (Level 2) [Member] | Commercial paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 272.3  
Significant other observable Inputs (Level 2) [Member] | Money market securities [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 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 465.5 1,276.7
Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
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] | General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
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]
   
Assets:    
Cash Equivalents 0  
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]
   
Assets:    
Cash Equivalents 0  
Available-for-sale securities:    
Available-for-sale securities 0 0
Significant unobservable Inputs (Level 3) [Member] | Commercial paper [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 0  
Significant unobservable Inputs (Level 3) [Member] | Money market securities [Member] | Fair Value, Measurements, Recurring [Member]
   
Assets:    
Cash Equivalents 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