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Asset Retirement Obligations (Tables)
 12 Months Ended
Dec. 31, 2011
Asset Retirement Obligations [Abstract]  
Schedule Of Asset Retirement Obligations
     2011     2010  
     (In thousands)  

ARO liability, January 1:

    $ 69,265      $ 56,404   

Accretion of discount

      3,838        2,937   

Liability incurred

      15,068 (1)      4,768   

Liability settled

      (1,009 )      (763 ) 

Revision of estimates

      9,284 (2)      5,919 (2) 
  

 

 

    

 

 

  

ARO liability, December 31:

      96,446        69,265   

Less current portion

      3,040        1,915   
  

 

 

    

 

 

  

Total long-term ARO liability

    $ 93,406      $ 67,350   
  

 

 

    

 

 

  

(1) Liability incurred in 2011 includes new wells acquired.

 

(2) Plugging liability estimates were revised upward in both 2011 and 2010 due to increases in the cost of services used to plug wells over the preceding years.