Summary of Significant Accounting Policies (Details Textual) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) shares	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) shares	Dec. 22, 2017	Dec. 31, 2016 USD ($)
Summary of Significant Accounting Policies
Total capitalized internal costs	$ 1,000	$ 1,200	$ 2,400	$ 2,100
Proved oil and gas properties	738,780		738,780		$ 658,519
Unproved oil and gas properties	53,865		53,865		50,377
Furniture, fixtures, and other equipment	3,407		3,407		3,270
Less - Accumulated depreciation, depletion, and amortization	(242,997)		(242,997)		(216,769)
Property and Equipment, Net	553,055		$ 553,055		495,397
Discount rate for estimated future net revenues from proved properties			10.00%
Write-down of oil and gas properties	0	0	$ 0	0
Allowance for doubtful accounts receivable, current	100		100		100
Accounts receivable, gross	17,400		17,400		20,100
Accounts receivable related to joint interest owners	1,100		1,100		2,100
Severance tax receivable	800		800		2,100
Other receivables	2,800		$ 2,800		3,000
Percentage of working interest in wells			100.00%
Total amount of supervision fees charged to wells	1,100	1,100	$ 2,200	2,300
Income Tax Expense (Benefit)	328	0	328	0
Previous Federal Corporate Tax Rate						0.35
New Federal Corporate Tax Rate						0.21
Trade accounts payable	16,015		16,015		20,884
Accrued operating expenses	2,316		2,316		3,490
Accrued payroll costs	2,945		2,945		5,334
Asset retirement obligation - current portion	303		303		2,109
Accrued non-income based taxes	5,137		5,137		3,898
Accrued corporate and legal fees	3,120		3,120		2,784
Other payables	5,514		5,514		5,938
Accounts payable and accrued liabilities	35,350		35,350		44,437
Cash and cash equivalents	6,611	6,627	6,611	6,627	7,806
Restricted Cash	220	179	220	179	220
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 6,831	$ 6,806	$ 6,831	$ 6,806	$ 8,026		$ 497
Purchase of treasury stock (shares) | shares			15,107		28,279
Other Commitment					$ 6,200
Lessee, Operating Lease, Term of Contract					3 years
Office Lease [Member]
Summary of Significant Accounting Policies
Other Commitment					$ 2,000
Minimum [Member]
Summary of Significant Accounting Policies
Estimated useful lives of property			2 years
Maximum [Member]
Summary of Significant Accounting Policies
Estimated useful lives of property			20 years