Other Operating Revenues and Expenses (Details) (USD $)	1 Months Ended			12 Months Ended
	Feb. 28, 2011 Drillingrig hp	Aug. 31, 2010	Jun. 30, 2010 well	Dec. 31, 2012	Dec. 31, 2011 well	Dec. 31, 2010
Sales of Assets and Impairments of Inventory
Gain on sales of assets				$ 1,496,000	$ 15,744,000	$ 3,680,000
Net marketing revenue				581,000	0	0
Total operating revenues				2,077,000	15,744,000	3,680,000
Other operating expenses
Loss on sales of assets				(523,000)	(945,000)	(1,655,000)
Impairment of inventory				(510,000)	(721,000)	(95,000)
Total operating expenses				(1,033,000)	(1,666,000)	(1,750,000)
Number of drilling rigs sold	2
Capacity of drilling rigs sold (in horsepower)	2,000
Total consideration received from sale of assets	22,000,000			3,778,000	13,902,000	77,216,000
Gain on sale of drilling rigs and related equipment	13,200,000
Consideration from sale of assets	11,000,000
Proceeds from the sale consisting of promissory note	11,000,000
Number of prospective wells sold					2
Gain (loss) on sale of wells			(1,400,000)		852,000
Number of operated wells in which interest was sold			22
Number of non-operated wells in which interest was sold			76
Net proceeds from sale of interests in wells		2,900,000	73,100,000
Customary adjustments from sale proceeds of interests in wells			$ 2,000,000