Summary of Significant Accounting Policies (Details Textual) $ in Thousands		3 Months Ended				6 Months Ended
	Aug. 03, 2021 USD ($)	Jun. 30, 2021 USD ($) MMBTU bbl $ / MMBTU $ / Boe shares	Mar. 31, 2021 shares	Jun. 30, 2020 USD ($) shares	Mar. 31, 2020 shares	Jun. 30, 2021 USD ($) MMBTU bbl $ / MMBTU $ / Boe shares	Jun. 30, 2020 USD ($) shares	Jul. 30, 2021 MMBTU bbl $ / MMBTU $ / Boe	Dec. 31, 2020 USD ($)
Summary of Significant Accounting Policies
Brent Spot Price		77	64			77
WTI Spot Price		74	59			74
Acquisition of oil and gas properties | $						$ 207	$ 3,394
Total capitalized internal costs | $		$ 1,200		$ 900		2,300	2,000
Proved oil and gas properties | $		1,372,163				1,372,163			$ 1,310,008
Unproved oil and gas properties | $		24,312				24,312			28,090
Furniture, fixtures, and other equipment | $		5,727				5,727			5,275
Less - Accumulated depreciation, depletion, and amortization | $		(830,749)				(830,749)			(801,279)
Net Furniture, Fixtures and other equipment | $		571,453				571,453			542,094
Write-down of oil and gas properties | $		0		260,342		0	355,948
Allowance for doubtful accounts receivable, current | $		100				100			100
Accounts receivable, gross | $		23,900				23,900			18,800
Accounts receivable related to joint interest owners | $		600				600			4,000
Severance tax receivable | $		1,000				1,000			2,400
Other receivables | $		400				$ 400			700
Percentage of working interest in wells						100.00%
Total amount of supervision fees charged to wells | $		1,200		900		$ 2,400	2,200
Provision (Benefit) for Income Taxes | $		0		22,420		0	21,179
Oil and gas sales | $		69,861		$ 24,846		156,602	$ 78,222
Trade accounts payable | $		8,736				8,736			15,930
Accrued operating expenses | $		2,873				2,873			2,491
Accrued payroll costs | $		2,579				2,579			3,771
Asset retirement obligation - current portion | $		515				515			441
Accrued non-income based taxes | $		2,517				2,517			1,819
Accrued corporate and legal fees | $		143				143			150
Other payables | $		6,524				6,524			2,389
Accounts payable and accrued liabilities | $		$ 23,887				$ 23,887			$ 26,991
Purchase of treasury stock (shares) | shares		13,969	60,177	1,098	26,675	74,146	27,773
Oil sales [Member]
Summary of Significant Accounting Policies
Oil and gas sales | $		$ 15,890		$ 5,265		$ 33,356	$ 23,315
Natural gas sales [Member]
Summary of Significant Accounting Policies
Oil and gas sales | $		46,791		18,103		109,705	49,574
NGL sales [Member]
Summary of Significant Accounting Policies
Oil and gas sales | $		$ 7,180		$ 1,478		$ 13,541	$ 5,333
Subsequent Event [Member] | Webb County Acquisition
Summary of Significant Accounting Policies
Wells Purchased	12
Acquisition of oil and gas properties | $	$ 24,000
Swap [Member] | Third Quarter 2021 [Member] | Swap Purchase | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								12,000
Derivative, Swap Type, Fixed Price | $ / Boe								72.76
Swap [Member] | Third Quarter 2021 [Member] | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		179,759				179,759
Derivative, Swap Type, Fixed Price | $ / Boe		51.19				51.19
Swap [Member] | Third Quarter 2021 [Member] | Oil Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								30,000
Derivative, Swap Type, Fixed Price | $ / Boe								70.75
Swap [Member] | Third Quarter 2021 [Member] | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		330,000				330,000
Derivative, Swap Type, Fixed Price		2.62				2.62
Swap [Member] | Third Quarter 2021 [Member] | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								610,000
Derivative, Swap Type, Fixed Price								4.00
Swap [Member] | Third Quarter 2021 [Member] | NGL Derivative
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		192,324				192,324
Derivative, Swap Type, Fixed Price		24.26				24.26
Swap [Member] | Fourth Quarter 2021 [Member] | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		191,412				191,412
Derivative, Swap Type, Fixed Price | $ / Boe		53.60				53.60
Swap [Member] | Fourth Quarter 2021 [Member] | Oil Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								81,250
Derivative, Swap Type, Fixed Price | $ / Boe								66.69
Swap [Member] | Fourth Quarter 2021 [Member] | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		290,000				290,000
Derivative, Swap Type, Fixed Price		2.69				2.69
Swap [Member] | Fourth Quarter 2021 [Member] | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								1,240,000
Derivative, Swap Type, Fixed Price								3.90
Swap [Member] | Fourth Quarter 2021 [Member] | NGL Derivative
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		192,324				192,324
Derivative, Swap Type, Fixed Price		24.26				24.26
Swap [Member] | First Quarter 2022 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		178,455				178,455
Derivative, Swap Type, Fixed Price | $ / Boe		45.77				45.77
Swap [Member] | First Quarter 2022 | Oil Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								45,000
Derivative, Swap Type, Fixed Price | $ / Boe								63.37
Swap [Member] | First Quarter 2022 | NGL Derivative
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		45,000				45,000
Derivative, Swap Type, Fixed Price		23.52				23.52
Swap [Member] | First Quarter 2022 | NGL Derivative | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								45,000
Derivative, Swap Type, Fixed Price								26.32
Swap [Member] | Second Quarter 2022 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		91,000				91,000
Derivative, Swap Type, Fixed Price | $ / Boe		54.00				54.00
Swap [Member] | Second Quarter 2022 | Oil Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								45,500
Derivative, Swap Type, Fixed Price | $ / Boe								62.00
Swap [Member] | Second Quarter 2022 | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								3,795,000
Derivative, Swap Type, Fixed Price								2.99
Swap [Member] | Second Quarter 2022 | NGL Derivative | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								45,500
Derivative, Swap Type, Fixed Price								26.32
Swap [Member] | Third Quarter 2022 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		200,100				200,100
Derivative, Swap Type, Fixed Price | $ / Boe		47.05				47.05
Swap [Member] | Third Quarter 2022 | Oil Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								46,000
Derivative, Swap Type, Fixed Price | $ / Boe								60.81
Swap [Member] | Third Quarter 2022 | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		2,100				2,100
Derivative, Swap Type, Fixed Price		2.50				2.50
Swap [Member] | Third Quarter 2022 | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								4,140,000
Derivative, Swap Type, Fixed Price								3.02
Swap [Member] | Third Quarter 2022 | NGL Derivative | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								46,000
Derivative, Swap Type, Fixed Price								26.32
Swap [Member] | Fourth Quarter 2022 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		138,000				138,000
Derivative, Swap Type, Fixed Price | $ / Boe		53.20				53.20
Swap [Member] | Fourth Quarter 2022 | Oil Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								46,000
Derivative, Swap Type, Fixed Price | $ / Boe								59.75
Swap [Member] | Fourth Quarter 2022 | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								2,760,000
Derivative, Swap Type, Fixed Price								3.14
Swap [Member] | Fourth Quarter 2022 | NGL Derivative | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl								46,000
Derivative, Swap Type, Fixed Price								26.32
Swap [Member] | First Quarter 2023 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | bbl		81,900				81,900
Derivative, Swap Type, Fixed Price | $ / Boe		55.70				55.70
Collar Contracts [Member] | Third Quarter 2021 [Member] | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		90,620				90,620
Derivative, Average Floor Price		34.34				34.34
Derivative, Average Cap Price		39.87				39.87
Collar Contracts [Member] | Third Quarter 2021 [Member] | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		8,185,175				8,185,175
Derivative, Average Floor Price		2.36				2.36
Derivative, Average Cap Price		2.82				2.82
Collar Contracts [Member] | Fourth Quarter 2021 [Member] | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		84,640				84,640
Derivative, Average Floor Price		34.70				34.70
Derivative, Average Cap Price		41.01				41.01
Collar Contracts [Member] | Fourth Quarter 2021 [Member] | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		8,991,000				8,991,000
Derivative, Average Floor Price		2.61				2.61
Derivative, Average Cap Price		2.98				2.98
Collar Contracts [Member] | First Quarter 2022 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		40,500				40,500
Derivative, Average Floor Price		40.00				40.00
Derivative, Average Cap Price		45.55				45.55
Collar Contracts [Member] | First Quarter 2022 | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		8,465,000				8,465,000
Derivative, Average Floor Price		2.72				2.72
Derivative, Average Cap Price		3.36				3.36
Collar Contracts [Member] | Second Quarter 2022 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		115,850				115,850
Derivative, Average Floor Price		39.25				39.25
Derivative, Average Cap Price		46.20				46.20
Collar Contracts [Member] | Second Quarter 2022 | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		5,246,500				5,246,500
Derivative, Average Floor Price		2.15				2.15
Derivative, Average Cap Price		2.60				2.60
Collar Contracts [Member] | Third Quarter 2022 | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		4,899,000				4,899,000
Derivative, Average Floor Price		2.39				2.39
Derivative, Average Cap Price		2.72				2.72
Collar Contracts [Member] | Fourth Quarter 2022 | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		4,545,076				4,545,076
Derivative, Average Floor Price		2.41				2.41
Derivative, Average Cap Price		2.88				2.88
Collar Contracts [Member] | Fourth Quarter 2022 | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								1,380,000
Derivative, Average Floor Price								2.90
Derivative, Average Cap Price								3.34
Collar Contracts [Member] | First Quarter 2023 | Natural Gas Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		4,297,000				4,297,000
Derivative, Average Floor Price		2.62				2.62
Derivative, Average Cap Price		3.11				3.11
Collar Contracts [Member] | First Quarter 2023 | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								1,350,000
Derivative, Average Floor Price								2.95
Derivative, Average Cap Price								3.51
Collar Contracts [Member] | Second Quarter 2023 | Oil Derivative Swaps [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU		36,400				36,400
Derivative, Average Floor Price		56.00				56.00
Derivative, Average Cap Price		63.20				63.20
Collar Contracts [Member] | Second Quarter 2023 | Natural Gas Derivative Swaps [Member] | Subsequent Event [Member]
Summary of Significant Accounting Policies
Oil and Gas Production Hedged Volumes | MMBTU								2,275,000
Derivative, Average Floor Price								2.40
Derivative, Average Cap Price								2.84
Minimum [Member]
Summary of Significant Accounting Policies
Estimated useful lives of property						2 years
Maximum [Member]
Summary of Significant Accounting Policies
Estimated useful lives of property						20 years