Note 6 - Long-term Debt (Details Textual) - Fifth Third Bank, National Association [Member] $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
Dec. 31, 2020 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Revolving Credit Facility [Member]
Line of Credit Facility, Maximum Borrowing Capacity	$ 40,000	$ 50,000	$ 40,000
Line of Credit Facility, Commitment Fee Amount	20,000
Debt Instrument, Face Amount	500,000		500,000
Long-term Debt, Gross	$ 0	0	$ 0
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage			0.50%
Debt Instrument, Covenant, Minimum Cash Threshold for Prepayment to be Due		$ 20,000
Revolving Credit Facility [Member] \| Maximum [Member]
Debt Instrument, Covenant, Maximum Total Debt to EBITDAX Ratio		3
Revolving Credit Facility [Member] \| Minimum [Member]
Debt Instrument, Covenant, Minimum Current Ratio		1
Revolving Credit Facility [Member] \| Fed Funds Effective Rate Overnight Index Swap Rate [Member]
Debt Instrument, Basis Spread on Variable Rate			0.50%
Revolving Credit Facility [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument, Basis Spread on Variable Rate			3.25%
Letter of Credit [Member] \| London Interbank Offered Rate (LIBOR), Applicable Margin [Member]
Debt Instrument, Basis Spread on Variable Rate			0.125%

The maximum total debt to EBITDAX ratio required by the debt agreement.

No definition available.

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- Definition

The minimum amount of cash threshold for debt prepayments to become due required by the debt agreement.

+ References

No definition available.

+ Details

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- Definition

The minimum current ratio required by the debt agreement.

+ References

No definition available.

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
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-SubTopic 210
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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 45
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- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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