Supplemental Disclosures (Details 1) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Supplemental disclosures of cash flow information
Increase in asset retirement obligations related to mineral properties	$ 2,484	$ 2,588
(Decrease) increase in asset retirement obligations related to support equipment and facilities	(138)	644
Increase (decrease) in liabilities for oil and natural gas properties capital expenditures	35,940	(7,849)
Decrease in liabilities for support equipment and facilities	(247)	(2,687)
Stock-based compensation expense recognized as liability	150	457
Decrease in liabilities for accrued cost to issue equity	(343)	0
Transfer of inventory from oil and natural gas properties	$ 74	$ 655