Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements (Details)

v3.3.1.900
Fair Value Measurements (Details) - USD ($)
$ in Millions
Feb. 29, 2016
May. 31, 2015
Available-for-sale securities:    
Available-for-sale securities $ 2,983.2 $ 3,595.6
Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 1,315.9 103.1
Available-for-sale securities:    
Available-for-sale securities 2,983.2 3,595.6
Other 13.8 14.2
Liabilities:    
Other long-term liabilities 13.8 14.2
Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 150.1 0.2
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
Other 13.8 14.2
Liabilities:    
Other long-term liabilities 13.8 14.2
Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 1,165.8 102.9
Available-for-sale securities:    
Available-for-sale securities 2,983.2 3,595.6
Other 0.0 0.0
Liabilities:    
Other long-term liabilities 0.0 0.0
Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0 0.0
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
Other 0.0 0.0
Liabilities:    
Other long-term liabilities 0.0 0.0
Commercial paper [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 965.8 15.0
Commercial paper [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0 0.0
Commercial paper [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 965.8 15.0
Commercial paper [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0 0.0
Time deposits [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 150.0  
Time deposits [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 150.0  
Time deposits [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0  
Time deposits [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0  
Money market securities [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.1 0.2
Money market securities [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.1 0.2
Money market securities [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0 0.0
Money market securities [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0 0.0
Corporate bonds [Member]    
Available-for-sale securities:    
Available-for-sale securities 110.4  
Corporate bonds [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities 110.4  
Corporate bonds [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities 0.0  
Corporate bonds [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities 110.4  
Corporate bonds [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities 0.0  
General obligation municipal bonds [Member]    
Available-for-sale securities:    
Available-for-sale securities 1,662.6 1,703.7
General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   55.1
Available-for-sale securities:    
Available-for-sale securities 1,662.6 1,703.7
General obligation municipal bonds [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   0.0
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
General obligation municipal bonds [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   55.1
Available-for-sale securities:    
Available-for-sale securities 1,662.6 1,703.7
General obligation municipal bonds [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   0.0
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
Pre-refunded municipal bonds [Member]    
Available-for-sale securities:    
Available-for-sale securities [1] 69.7 102.7
Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   20.5
Available-for-sale securities:    
Available-for-sale securities 69.7 102.7
Pre-refunded municipal bonds [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   0.0
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
Pre-refunded municipal bonds [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   20.5
Available-for-sale securities:    
Available-for-sale securities 69.7 102.7
Pre-refunded municipal bonds [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   0.0
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
Revenue municipal bonds [Member]    
Available-for-sale securities:    
Available-for-sale securities 951.3 963.6
Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   12.3
Available-for-sale securities:    
Available-for-sale securities 951.3 963.6
Revenue municipal bonds [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   0.0
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
Revenue municipal bonds [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   12.3
Available-for-sale securities:    
Available-for-sale securities 951.3 963.6
Revenue municipal bonds [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents   0.0
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
U.S. government agency securities [Member]    
Available-for-sale securities:    
Available-for-sale securities 121.2  
U.S. government agency securities [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 200.0  
Available-for-sale securities:    
Available-for-sale securities 121.2  
U.S. government agency securities [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0  
Available-for-sale securities:    
Available-for-sale securities 0.0  
U.S. government agency securities [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 200.0  
Available-for-sale securities:    
Available-for-sale securities 121.2  
U.S. government agency securities [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Assets:    
Cash Equivalents 0.0  
Available-for-sale securities:    
Available-for-sale securities 0.0  
Variable rate demand notes [Member]    
Available-for-sale securities:    
Available-for-sale securities 68.0 825.6
Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities 68.0 825.6
Variable rate demand notes [Member] | Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities 0.0 0.0
Variable rate demand notes [Member] | Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities 68.0 825.6
Variable rate demand notes [Member] | Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]    
Available-for-sale securities:    
Available-for-sale securities $ 0.0 $ 0.0
[1] Pre-refunded municipal bonds are secured by an escrow fund of U.S. government obligations.