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Fair Value of Financial Instruments (Details) (USD $)
3 Months Ended 6 Months Ended
Jun. 30, 2012
Jun. 30, 2011
Jun. 30, 2012
Jun. 30, 2011
Fair Value of Financial Instruments [Abstract]        
Asset retirement obligations, additional amount measured during the period $ 0 $ 0 $ 0 $ 0