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Derivatives (Details 4) (USD $) In Thousands, unless otherwise specified |  |  | 3 Months Ended
--- | --- | --- | ---
Mar. 31, 2012 | Dec. 31, 2011 | Mar. 31, 2012 Mark-to-Market on Series F Agreement [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |  |
Mark-to-Market of the Series F Agreement |  |  | $ 416
Reconciliation of liabilities classified as Level 3 |  |  |
Ending liability balance | (1,251) | (1,667) |
Total unrealized gains: |  |  |
Ending liability balance | $ (1,251) | $ (1,667) |

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