|
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 |