|
Variable Interests and Variable Interest Entities (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
6 Months Ended | |
|---|---|---|
|
Jun. 30, 2013
|
Jun. 30, 2012
|
|
| Schedule of Equity Method Investments [Line Items] | ||
| Payments made to Pure Air | $ 6.4 | $ 10.7 |