Fair Value Measurements (Details) (USD $)
In Millions, unless otherwise specified |
Aug. 31, 2012
|
May 31, 2012
|
---|---|---|
Available-for-sale securities: | ||
Available-for-sale securities | $ 3,407.9 | $ 3,059.0 |
Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 3,407.9 | 3,059.0 |
Other securities | 10.2 | 9.2 |
Liabilities: | ||
Other long-term liabilities | 10.2 | 9.2 |
General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 1,411.3 | 1,333.9 |
Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 242.0 | 334.3 |
Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 601.2 | 501.0 |
Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 1,153.4 | 889.8 |
Quoted prices in active markets (Level 1) [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | ||
Other securities | 10.2 | 9.2 |
Liabilities: | ||
Other long-term liabilities | 10.2 | 9.2 |
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 | ||
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 | ||
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 | ||
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 | ||
Significant other observable Inputs (Level 2) [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 3,407.9 | 3,059.0 |
Other securities | ||
Liabilities: | ||
Other long-term liabilities | ||
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 | 1,411.3 | 1,333.9 |
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 | 242.0 | 334.3 |
Significant other observable Inputs (Level 2) [Member] | Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | 601.2 | 501.0 |
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 | 1,153.4 | 889.8 |
Significant unobservable Inputs (Level 3) [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | ||
Other securities | ||
Liabilities: | ||
Other long-term liabilities | ||
Significant unobservable Inputs (Level 3) [Member] | General obligation municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | ||
Significant unobservable Inputs (Level 3) [Member] | Pre-refunded municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | ||
Significant unobservable Inputs (Level 3) [Member] | Revenue municipal bonds [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities | ||
Significant unobservable Inputs (Level 3) [Member] | Variable rate demand notes [Member] | Fair Value, Measurements, Recurring [Member]
|
||
Available-for-sale securities: | ||
Available-for-sale securities |