Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Oil and gas sales	$ 72,064	$ 52,752
Property and Equipment
Proved oil and gas properties	1,005,988		$ 925,865
Unproved oil and gas properties	64,797		56,715
Furniture, fixtures, and other equipment	3,668		3,520
Less - Accumulated depreciation, depletion, and amortization	(306,609)		(284,804)
Net Furniture, Fixtures and other equipment	767,844		701,296
Accounts Payable and Accrued Liabilities
Trade accounts payable	20,728		32,683
Accrued operating expenses	3,258		3,549
Accrued compensation costs	2,066		4,785
Asset retirement obligation - current portion	284		302
Accrued non-income based taxes	2,533		3,583
Accrued corporate and legal fees	335		534
Other payables	2,774		3,485
Total accounts payable and accrued liabilities	31,978		$ 48,921
Oil sales [Member]
Disaggregation of Revenue [Line Items]
Oil and gas sales	14,607	11,439
Natural gas sales [Member]
Disaggregation of Revenue [Line Items]
Oil and gas sales	51,304	35,753
NGL sales [Member]
Disaggregation of Revenue [Line Items]
Oil and gas sales	$ 6,154	$ 5,560