Supplemental Information on Oil & Natural Gas Exploration and Production Activities (unaudited) (Details 2)	12 Months Ended
	Dec. 31, 2013 Boe	Dec. 31, 2012 Boe	Dec. 31, 2011 Boe
Changes in estimated net proved developed crude oil and natural gas reserves
Reserves at the beginning of the period	4,087	21,757	86,230
Reserves sold	(140)		(44,880)
Revisions of previous estimates	(1,107)	(11,146)	(1,071)
Production	(2,340)	(6,524)	(18,522)
Reserves at the end of the period	500	4,087	21,757
Rate at which proved natural gas reserves (Mcf) are converted to equivalent barrels of crude oil (Bbl)	6
Oil
Changes in estimated net proved developed crude oil and natural gas reserves
Reserves at the beginning of the period	920	6,640	47,700
Reserves sold	(100)		(32,473)
Revisions of previous estimates	6	(2,769)	1,469
Production	(766)	(2,951)	(10,056)
Reserves at the end of the period	60	920	6,640
Average prices used in calculations	96.90	94.68	95.84
Gas
Changes in estimated net proved developed crude oil and natural gas reserves
Reserves at the beginning of the period	19,000	90,700	231,180
Reserves sold	(238)		(74,438)
Revisions of previous estimates	(6,679)	(50,258)	(15,246)
Production	(9,443)	(21,442)	(50,796)
Reserves at the end of the period	2,640	19,000	90,700
Average prices used in calculations	3.67	2.76	4.15