Long-Term Debt (Details) $ in Thousands				3 Months Ended		6 Months Ended
	Apr. 16, 2021 USD ($)	Nov. 02, 2020 USD ($)	Dec. 15, 2017 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Bank Borrowings
Long-term Debt, excluding current maturities				$ 393,446		$ 393,446		$ 424,905
Gross interest expense including amortization of debt issuance costs				7,436	$ 8,026	14,454	$ 16,433
Capitalized interest on our unproved properties				0	0	0	0
Payments of Debt Issuance Costs						2,400	0
Write off of Debt Issuance Cost						229	459
Second Lien [Abstract]
Long-term debt, gross				398,000		398,000		430,000
New Credit Facility [Member]
Bank Borrowings
Debt Issuance Costs, Net				3,000		3,000		1,400
Second Lien Notes [Member]
Bank Borrowings
Debt Issuance Costs, Net				3,397		3,397		3,800
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	4,600	9,200	9,500
Second Lien [Abstract]
Long-term debt, gross			200,000
Debt Instrument, Unamortized Discount			(2,000)	(1,157)		(1,157)		(1,295)
Additional notes issuable			$ 100,000
Additional interest in the event of default			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%
Discount Rate for Estimated Future Net Revenues for Proved Properties at 9%			9.00%
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				195,400		195,400
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				198,000		198,000		$ 230,000
Line of Credit Facility, Current Borrowing Capacity	$ 300,000	$ 310,000
Line of Credit, Basis Point Increase	50
Line of Credit, Covenant, Debt to EBITDA Ratio, On or Before December 31, 2020		3.50
Line of Credit, Covenant, Debt to EBITDA Ratio, On or Before December 31, 2021	3.25
Line of Credit, Covenant, Debt to EBITDA Ratio, On or Before March 31, 2022	3.00
Line of Credit, Minimum Rolling Hedge Requirement	0.50
Line of Credit, Required Security Interest on Oil and Gas Properties	90.00%	85.00%
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, Covenant, Current Ratio, Minimum	1.00
Gross interest expense including amortization of debt issuance costs				2,800	$ 3,500	5,300	$ 6,900
Payments of Debt Issuance Costs				$ 2,400
Write off of Debt Issuance Cost						$ 200
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	0.0225
Debt Instrument Escalating Rates for Eurodollar Rate Loans	0.0325
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	0.0325
Debt Instrument Escalating Rates for Eurodollar Rate Loans	0.0425