Supplemental Disclosures (Details 1) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Supplemental disclosures of cash flow information
Cash paid for interest expense, net of amounts capitalized	$ 2,617	$ 3,667
Asset retirement obligations related to mineral properties	1,487	3,305
Asset retirement obligations related to support equipment and facilities	89	132
(Decrease) increase in liabilities for oil and natural gas properties capital expenditures	(30,282)	43,692
Increase in liabilities for support equipment and facilities	2,525	2,488
Stock-based compensation expense recognized as liability	191	789
Transfer of inventory from oil and natural gas properties	$ 586	$ 300