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Fair Value Measurements (Tables)
9 Months Ended
Sep. 30, 2011
Fair Value Measurements [Abstract] 
Fair value of plan assets
                                 
    Fair Value Measurements at September 30, 2011  
            Quoted Prices in             Significant  
            Active Markets for     Significant Other     Unobservable  
            Identical Assets     Observable Inputs     Inputs  
Assets   Total     (Level 1)     (Level 2)     (Level 3)  
Money Market Funds
  $ 0.1     $ 0.1     $     $  
Natural Gas Derivatives
  $     $     $     $  
Oil Derivatives
  $     $     $     $