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Asset Retirement Obligations (Details) (USD $)
In Thousands, unless otherwise specified
6 Months Ended 12 Months Ended
Jun. 30, 2012
Dec. 31, 2011
Reconciliation of the total liability for asset retirement obligations [Roll Forward]    
Beginning asset retirement obligation $ 510 $ 303
Accretion of discount 16 23
Liabilities incurred 93 187
Liabilities sold 0 (3)
Ending asset retirement obligation 619 510
Mining properties [Member]
   
Reconciliation of the total liability for asset retirement obligations [Roll Forward]    
Ending asset retirement obligation 155 149
Oil & Gas wells [Member]
   
Reconciliation of the total liability for asset retirement obligations [Roll Forward]    
Ending asset retirement obligation $ 464 $ 361