Supplemental Disclosures (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental disclosures of cash flow information
Cash paid for income taxes	$ 0	$ 0	$ 2,895
Cash paid for interest expense, net of amounts capitalized	29,474	32,760	27,464
Increase in asset retirement obligations related to mineral properties	2,614	4,385	3,817
Increase (decrease) in asset retirement obligations related to midstream properties	686	(60)	222
(Decrease) increase in liabilities for oil and natural gas properties capital expenditures	(16,802)	48,929	1,775
Increase (decrease) in liabilities for midstream properties capital expenditures	2,499	(955)	(588)
Issuance of restricted stock units for director and advisor services	0	0	992
Stock-based compensation (benefit) expense recognized as liability	(1,069)	362	569
(Decrease) increase in liabilities for accrued cost to issue equity	0	(343)	343
Increase in liabilities for accrued cost to issue debt	232	0	0
Transfer of inventory from (to) oil and natural gas properties	409	(374)	395
Transfer of inventory to midstream and other property and equipment	$ 0	$ (317)	$ 0