Summary of Significant Accounting Policies (Details Textual) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018 USD ($) shares	Mar. 31, 2017 USD ($)	Dec. 31, 2017 USD ($) shares	Apr. 20, 2018 USD ($)	Dec. 22, 2017	Dec. 31, 2016 USD ($)
Summary of Significant Accounting Policies
Total capitalized internal costs	$ 1,400	$ 900
Proved oil and gas properties	664,742		$ 658,519
Unproved oil and gas properties	55,725		50,377
Furniture, fixtures, and other equipment	3,361		3,270
Less - Accumulated depreciation, depletion, and amortization	(229,901)		(216,769)
Property and Equipment, Net	$ 493,927		495,397
Discount rate for estimated future net revenues from proved properties	10.00%
Write-down of oil and gas properties	$ 0	0
Allowance for doubtful accounts receivable, current	100		100
Accounts receivable, gross	17,000		20,100
Accounts receivable related to joint interest owners	2,700		2,100
Severance tax receivable	1,100		2,100
Other receivables	$ 300		3,000
Percentage of working interest in wells	100.00%
Total amount of supervision fees charged to wells	$ 1,100	1,200
Previous Federal Corporate Tax Rate					0.35
New Federal Corporate Tax Rate					0.21
Trade accounts payable	15,440		20,884
Accrued operating expenses	2,964		3,490
Accrued payroll costs	1,956		5,334
Asset retirement obligation - current portion	467		2,109
Accrued non-income based taxes	4,058		3,898
Accrued corporate and legal fees	2,982		2,784
Other payables	4,422		5,938
Accounts payable and accrued liabilities	32,289		44,437
Cash and cash equivalents	237	168	7,806
Restricted Cash	220	832	220
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 457	$ 1,000	$ 8,026			$ 497
Purchase of treasury stock (shares) | shares	10,458		28,279
Other Commitment			$ 6,200
Lessee, Operating Lease, Term of Contract			3 years 5 months
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
Subsequent Event [Member] | New Credit Facility [Member] | Line of Credit [Member]
Summary of Significant Accounting Policies
Line of Credit Facility, Current Borrowing Capacity				$ 330,000
Office Lease [Member]
Summary of Significant Accounting Policies
Other Commitment			$ 2,000