|
Fair Value Measurements (Details) (USD $)
In Millions |
May 31, 2011
|
May 31, 2010
|
|---|---|---|
| Available-for-sale securities: | ||
| Available-for-sale securities | $ 2,737.2 | $ 2,151.8 |
| Other securities | 8.9 | 7.3 |
| Liabilities | ||
| Other long-term liabilities | 8.9 | 7.3 |
|
Quoted prices in active markets (Level 1) [Member]
|
||
| Available-for-sale securities: | ||
| Other securities | 8.9 | 7.3 |
|
Quoted prices in active markets (Level 1) [Member]
|
||
| Liabilities | ||
| Other long-term liabilities | 8.9 | 7.3 |
|
General obligation municipal bonds [Member] | Significant other observable Inputs (Level 2) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 1,050.5 | 984.5 |
|
Pre-refunded municipal bonds [Member] | Significant other observable Inputs (Level 2) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 484.7 | 559.3 |
|
Revenue municipal bonds [Member] | Significant other observable Inputs (Level 2) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 373.7 | 381.7 |
|
Variable rate demand notes [Member] | Significant other observable Inputs (Level 2) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 828.3 | 226.3 |
|
Significant other observable Inputs (Level 2) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 2,737.2 | 2,151.8 |
|
General obligation municipal bonds [Member] | Significant unobservable Inputs (Level 3) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 0 | 0 |
|
Pre-refunded municipal bonds [Member] | Significant unobservable Inputs (Level 3) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 0 | 0 |
|
Revenue municipal bonds [Member] | Significant unobservable Inputs (Level 3) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 0 | 0 |
|
Variable rate demand notes [Member] | Significant unobservable Inputs (Level 3) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 0 | 0 |
|
Significant unobservable Inputs (Level 3) [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 0 | 0 |
| Other securities | 0 | 0 |
|
Significant unobservable Inputs (Level 3) [Member]
|
||
| Liabilities | ||
| Other long-term liabilities | 0 | 0 |
|
General obligation municipal bonds [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 1,050.5 | 984.5 |
|
Pre-refunded municipal bonds [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 484.7 | 559.3 |
|
Revenue municipal bonds [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | 373.7 | 381.7 |
|
Variable rate demand notes [Member]
|
||
| Available-for-sale securities: | ||
| Available-for-sale securities | $ 828.3 | $ 226.3 |