Long-Term Debt (Details) $ in Thousands				12 Months Ended
	Nov. 06, 2018 USD ($)	Dec. 15, 2017 USD ($)	Apr. 19, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Apr. 20, 2018 USD ($)
Bank Borrowings
Long-Term Debt, excluding current maturities				$ 387,988	$ 265,325
Interest expense including commitment fees and amortization of debt issuance costs relating to the credit facility				27,666	15,070
Write off of Deferred Debt Issuance Cost				0	2,676
Second Lien
Long-term Debt, Gross				$ 395,000	273,000
Discount Rate for Estimated Future Net Revenues from Proved Properties				10.00%
Line of Credit [Member]
Bank Borrowings
Capitalized interest on our unproved properties				$ 900	800
New Credit Facility [Member]
Bank Borrowings
Debt Issuance Costs, Net				(4,500)	(5,500)
New Credit Facility [Member] | Line of Credit [Member]
Bank Borrowings
Long-Term Debt, excluding current maturities				195,000	73,000
Line of Credit, current borrowing base	$ 410,000					$ 330,000
Decrease in applicable margin to calculate interest	25
Line of Credit Facility, Maximum Borrowing Capacity			$ 600,000
Line of Credit, Letters of Credit Issuable			$ 25,000
Line of Credit Facility, Commitment Fee Percentage			0.50%
Line of Credit, Additional Interest Due to Payment Default			2.00%
Line of Credit, Required Security Interest on Oil and Gas Properties			85.00%
Line of Credit, Covenant, Debt to EBITDA Ratio, Minimum			4.0
Line of Credit, Covenant, Current Ratio, Minimum			1.0
Interest expense including commitment fees and amortization of debt issuance costs relating to the credit facility				8,000	14,900
Write off of Deferred Debt Issuance Cost					2,700
Commitment fees included in interest expense, net				1,100	400
New Credit Facility [Member] | Line of Credit [Member] | Minimum [Member] | Alternative Base Interest Rate [Member]
Bank Borrowings
Debt Instrument escalating basis spread on base rate	0.0100
Debt instrument escalating rates for eurodollar rate loans	0.02
New Credit Facility [Member] | Line of Credit [Member] | Maximum [Member] | Alternative Base Interest Rate [Member]
Bank Borrowings
Debt Instrument escalating basis spread on base rate	0.0200
Debt instrument escalating rates for eurodollar rate loans	0.0300
Second Lien Notes [Member]
Bank Borrowings
Debt Issuance Costs, Net				(5,230)	(5,683)
Long-Term Debt, excluding current maturities		$ 198,000		200,000	200,000
Debt Instrument escalating basis spread on base rate		50
Additional interest in the event of default		0.020
Interest expense including commitment fees and amortization of debt issuance costs relating to the credit facility				20,500	800
Second Lien
Long-term Debt, Gross		$ 200,000
Debt Instrument, Unamortized Discount		(2,000)		$ (1,782)	$ (1,992)
Additional notes issuable		$ 100,000
Make whole premium during years 1 and 2		0.02
Make whole premium during year 3		0.02
Make whole premium during year 4		0.01
Second Lien, Required Security Interest on Proved Reserves		85.00%
Second Lien, Required Security Interest on Oil and Gas Properties		85.00%
Second Lien, Asset Coverage Ratio, Minimum		1.3
Discount Rate for Estimated Future Net Revenues from Proved Properties				10.00%
Second Lien, Covenant, Debt to EBITDA Ratio, Minimum		4.5
Long-term Debt				$ 193,000
Second Lien Notes [Member] | Alternative Base Interest Rate [Member]
Bank Borrowings
Debt Instrument escalating basis spread on base rate		0.065
Second Lien Notes [Member] | London Interbank Offered Rate (LIBOR) [Member]
Bank Borrowings
Debt Instrument escalating basis spread on base rate		0.075