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Asset Retirement Obligations (Tables)
 6 Months Ended
Jun. 30, 2011
Asset Retirement Obligations (Tables) [Abstract]  
Information related to asset retirement obligation
         
Balance at December 31, 2010
  $ 173,673  
Additions to asset retirement obligations
    268  
Accretion expense
    5,253  
Liabilities settled
    (1,727 )
 
     
Balance at June 30, 2011
  $ 177,467