Fair Value Measurements (Details) (USD $)
In Millions, unless otherwise specified |
Feb. 29, 2012
|
May 31, 2011
|
---|---|---|
Available-for-sale securities: | ||
Available-for-sale securities | $ 3,619.1 | $ 2,737.2 |
Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 3,619.1 | 2,737.2 |
Other securities | 9.3 | 8.9 |
Liabilities: | ||
Other long-term liabilities | 9.3 | 8.9 |
General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 1,099.8 | 1,050.5 |
Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 365.7 | 484.7 |
Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 416.4 | 373.7 |
Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 1,737.2 | 828.3 |
Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 0 | 0 |
Other securities | 9.3 | 8.9 |
Liabilities: | ||
Other long-term liabilities | 9.3 | 8.9 |
Quoted prices in active markets (Level 1) [Member] | General obligation 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] | 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]
|
||
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]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 3,619.1 | 2,737.2 |
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]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 1,099.8 | 1,050.5 |
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 | 365.7 | 484.7 |
Significant other observable Inputs (Level 2) [Member] | Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 416.4 | 373.7 |
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 | 1,737.2 | 828.3 |
Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
|
||
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]
|
||
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]
|
||
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 |