|
Commitments and Contingencies (Details 2) (USD $)
|
Dec. 31, 2011
plan
|
Dec. 31, 2010
|
|---|---|---|
| Commitments and Contingencies | ||
| Letters of credit outstanding | $ 75,000,000 | $ 71,000,000 |
| Number of US pension plans that are a LOC beneficiary | 1 |