Decommissioning Liabilities (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Summary of the activity for the Company's decommissioning liabilities
Decommissioning liabilities	$ 3,600,000
Decommissioning liabilities, December 31, 2011 and 2010, respectively	123,176,000	117,716,000
Liabilities acquired and incurred	3,573,000
Liabilities settled	(4,624,000)
Accretion	3,260,000	5,038,000
Revision estimated liabilities	(34,373,000)	(292,000)
Total decommissioning liabilities, June 30, 2012 and 2011, respectively	91,012,000	122,462,000
Less: current portion of decommissioning liabilities at June 30, 2012 and 2011, respectively		17,090,000	14,956,000
Long-term decommissioning liabilities, June 30, 2012 and 2011, respectively	$ 91,012,000	$ 105,372,000	$ 108,220,000