Debt Instrument, Payment Due Within Six Months

No definition available.

Name:	tgc_DebtInstrumentPaymentDueWithinSixMonths
Namespace Prefix:	tgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Inccrease Operating Lease, Right-of-Use Asset

+ References

No definition available.

+ Details

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Namespace Prefix:	tgc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Lessee, Operating Lease, Interest rate

+ References

No definition available.

+ Details

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Namespace Prefix:	tgc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line Of Credit Facility, Covenant, Current Ratio

+ References

No definition available.

+ Details

Name:	tgc_LineOfCreditFacilityCovenantCurrentRatio
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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility, Covenant, Funded Debt To Ebitda

+ References

No definition available.

+ Details

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Namespace Prefix:	tgc_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility, Covenant, Interest Coverage

+ References

No definition available.

+ Details

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Namespace Prefix:	tgc_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

The average effective interest rate during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Term of lessee's finance lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Discount rate used by lessee to determine present value of operating lease payments.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)(3)
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum amount borrowed under the credit facility at any time during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumAmountOutstandingDuringPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of revenue and income classified as other.

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-Name Accounting Standards Codification
-Topic 944
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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=tgc_PaycheckProtectionProgramLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=tgc_ProsperityBankMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=tgc_LoansAndLettersOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
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- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_VehiclesMember
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Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
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Long-Term Debt And Lease Liabilities (Narrative) (Details)		3 Months Ended	9 Months Ended
	May 01, 2020 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Office [Member]
Debt Instrument [Line Items]
Term of contract			39 months
Lease renewal term			12 months
Increased operating lease right of use			$ 63,000
Paycheck Protection Program Loan [Member]
Debt Instrument [Line Items]
Payments due within first six months of the loan	$ 0
Payment term			18 months
Prosperity Bank [Member]
Debt Instrument [Line Items]
Interest rate			3.75%
Credit facility current borrowing capacity			$ 3,100,000
Credit facility amount outstanding			0	$ 0
Credit limit			$ 1,442,000
Borrowing rate			3.75%
Prosperity Bank [Member] \| Loans And Letters Of Credit [Member]
Debt Instrument [Line Items]
Credit facility maximum borrowing capacity			$ 50,000,000
Prosperity Bank [Member] \| Paycheck Protection Program Loan [Member]
Debt Instrument [Line Items]
Interest rate	1.00%
Credit limit	$ 166,000
Maturity date			May 01, 2022
Maximum [Member] \| Vehicles [Member]
Debt Instrument [Line Items]
Term of contract			36 months
Discount rate			6.50%
Maximum [Member] \| Prosperity Bank [Member]
Debt Instrument [Line Items]
Funded debt to EBITDA			3.5
Minimum [Member] \| Vehicles [Member]
Debt Instrument [Line Items]
Term of contract			18 months
Discount rate			5.00%
Minimum [Member] \| Prosperity Bank [Member]
Debt Instrument [Line Items]
Current ratio			1
Interest coverage			3.0
Scenario, Forecast [Member] \| Prosperity Bank [Member] \| Paycheck Protection Program Loan [Member]
Debt Instrument [Line Items]
Other Income		$ 166,000