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Property, Plant And Equipment (Narrative) (Details) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2012
Mar. 31, 2011
Property, Plant and Equipment [Line Items]    
Impairment of oil and gas properties $ 368 $ 1,381
Unproved Oil And Gas Properties [Member]
   
Property, Plant and Equipment [Line Items]    
Impairment of oil and gas properties $ 400 $ 1,400