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Fair Value Measurements on a Recurring Basis (Tables)
6 Months Ended
Jun. 30, 2011
Notes To Financial Statements [Abstract]  
Fair Value, Measurement Inputs, Disclosure [Text Block]
The following presents the fair value hierarchy for assets and liabilities measured at fair value on a recurring basis:
 
   
June 30, 2011
   
Level 2
 
Netting (1)
 
Total
   
(in thousands)
Assets:
         
Commodity derivatives
 $440,485  $(269,869) $170,616 
              
Liabilities:
            
Commodity derivatives
 $470,024  $(269,869) $200,155 
 
(1)
Represents counterparty netting under agreements governing such derivatives.