Long-Term Debt (Details) $ in Thousands			3 Months Ended		6 Months Ended
	May 12, 2020 USD ($)	Dec. 15, 2017 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Apr. 19, 2017 USD ($)
Bank Borrowings
Long-term Debt, excluding current maturities			$ 464,390		$ 464,390		$ 472,900
Gross interest expense including amortization of debt issuance costs			8,026	$ 9,306	16,433	$ 18,065
Capitalized interest on our unproved properties			0	100	0	200
Second Lien [Abstract]
Long-term debt, gross			470,000		470,000		479,000
New Credit Facility [Member]
Bank Borrowings
Debt Issuance Costs, Net			2,000		2,000		3,100
Second Lien Notes [Member]
Bank Borrowings
Debt Issuance Costs, Net			4,185		4,185		4,550
Long-term Debt, excluding current maturities		$ 198,000	200,000		200,000		200,000
Gross interest expense including amortization of debt issuance costs			4,600	5,500	9,500	10,800
Second Lien [Abstract]
Long-term debt, gross		200,000
Debt Instrument, Unamortized Discount		(2,000)	(1,425)		(1,425)		(1,550)
Additional notes issuable		$ 100,000
Additional interest in the event of default		0.020
Make whole premium during year 3		0.020
Make whole premium during year 4		0.010
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		1.25
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, net			194,400		194,400
Second Lien Notes [Member] | London Interbank Offered Rate (LIBOR) [Member]
Bank Borrowings
Debt instrument escalating basis spread on base rate		0.075
Second Lien Notes [Member] | Alternative Base Interest Rate [Member]
Bank Borrowings
Debt instrument escalating basis spread on base rate		0.065
Line of Credit [Member] | New Credit Facility [Member]
Bank Borrowings
Long-term Debt, excluding current maturities			270,000		270,000		$ 279,000
Line of Credit Facility, Current Borrowing Capacity	$ 330,000
Increase in Applicable Margin, Basis Points	75
Anti-Cash Hoarding Provision, Defensive Draw, Cash Limit	$ 30,000
Anti-Cash Hoarding Provision, Defensive Draw, Borrowing Base Percent Limit	0.10
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			$ 3,500	$ 4,000	$ 6,900	$ 7,500
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	0.0175
Debt Instrument Escalating Rates for Eurodollar Rate Loans	0.0275
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	0.0275
Debt Instrument Escalating Rates for Eurodollar Rate Loans	0.0375