Long-Term Debt (Details) $ in Thousands			3 Months Ended		6 Months Ended
	Dec. 15, 2017 USD ($)	Apr. 19, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Apr. 20, 2018 USD ($)	Dec. 31, 2017 USD ($)
Bank Borrowings
Long-term Debt, excluding current maturities			$ 274,577		$ 274,577			$ 265,325
Gross interest expense including amortization of debt issuance costs			6,585	$ 4,642	12,474	$ 8,249
Commitment fees included in interest expense, net			300	100	600	200
Capitalized interest on our unproved properties			300	200	700	400
Second Lien [Abstract]
Long-term debt, gross			282,000		282,000			273,000
New Credit Facility [Member]
Bank Borrowings
Debt Issuance Costs, Net			4,900		4,900			5,500
Second Lien Notes [Member]
Bank Borrowings
Debt Issuance Costs, Net			5,534		5,534			5,683
Long-term Debt, excluding current maturities	$ 198,000		200,000		200,000			200,000
Debt instrument escalating basis spread on base rate	50
Gross interest expense including amortization of debt issuance costs			5,200		10,000
Second Lien [Abstract]
Long-term debt, gross	$ 200,000
Debt Instrument, Unamortized Discount	(2,000)		(1,889)		(1,889)			(1,992)
Additional notes issuable	$ 100,000
Additional interest in the event of default	0.020
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
Second Lien, Covenant, Debt to EBITDA Ratio, Minimum	4.5
Long-term debt, net			192,600		192,600
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
Line of Credit [Member] | New Credit Facility [Member]
Bank Borrowings
Long-term Debt, excluding current maturities			82,000		82,000			$ 73,000
Line of Credit Facility, Current Borrowing Capacity							$ 330,000
Decrease in applicable margin to calculate interest							50
Line of Credit Facility, Maximum Borrowing Capacity		$ 600,000
Line of Credit, Letters of Credit Issuable		$ 25,000
Commitment fee basis points for the credit facility		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
Gross interest expense including amortization of debt issuance costs			$ 1,600	$ 4,800	$ 3,100	$ 8,500
Line of Credit [Member] | New Credit Facility [Member] | Minimum [Member] | Alternative Base Interest Rate [Member]
Bank Borrowings
Debt instrument escalating basis spread on base rate		0.0125
Debt Instrument Escalating Rates for Eurodollar Rate Loans		0.0225
Line of Credit [Member] | New Credit Facility [Member] | Maximum [Member] | Alternative Base Interest Rate [Member]
Bank Borrowings
Debt instrument escalating basis spread on base rate		0.0225
Debt Instrument Escalating Rates for Eurodollar Rate Loans		0.0325