Refers to the annual percent of decline in premium prepayments.

No definition available.

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Namespace Prefix:	metc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Annual percentage of premium prepayment.

+ References

No definition available.

+ Details

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Namespace Prefix:	metc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of monthly installments under a debt agreement.

+ References

No definition available.

+ Details

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Namespace Prefix:	metc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number of installments.

+ References

No definition available.

+ Details

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Namespace Prefix:	metc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- 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
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Data Type:	num:percentItemType
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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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-Paragraph 1
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+ Details

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

- 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_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
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 borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ 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)(3)
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+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=metc_EquipmentLoanMember
Namespace Prefix:
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Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=metc_KeybankNationalAssociationMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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Balance Type:
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Period Type:

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Name:	us-gaap_VariableRateAxis=us-gaap_FederalFundsEffectiveSwapRateMember
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Balance Type:
Period Type:

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Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
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Data Type:	na
Balance Type:
Period Type:

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Note 4 - Debt (Details) - USD ($) $ in Millions			3 Months Ended
Note 4 - Debt (Details) - USD ($) $ in Millions	Apr. 16, 2020	Nov. 02, 2018	Mar. 31, 2021
Equipment Loan
Debt
Long-term Debt, Total			$ 3.4
KeyBank National Association \| Revolving Credit Facility
Debt
Line of Credit Facility, Maximum Borrowing Capacity		$ 30.0
Amount of remaining availability			13.6
Outstanding on Revolving Credit Facility			11.6
KeyBank National Association \| Revolving Credit Facility \| London Interbank Offered Rate (LIBOR)
Debt
Debt Instrument, Basis Spread on Variable Rate		2.00%
KeyBank National Association \| Revolving Credit Facility \| Base Rate
Debt
Debt Instrument, Basis Spread on Variable Rate		1.50%
KeyBank National Association \| Revolving Credit Facility \| Fed Funds Effective Rate Overnight Index Swap Rate
Debt
Debt Instrument, Basis Spread on Variable Rate		0.50%
KeyBank National Association \| Letter of Credit
Debt
Line of Credit Facility, Maximum Borrowing Capacity		$ 3.0
KeyBank National Association \| Term Loan
Debt
Debt Instrument, Face Amount		$ 10.0
Debt Instrument, Monthly Installment, Amount			278.0
Long-term Debt, Total			$ 5.9
KeyBank National Association \| Term Loan \| London Interbank Offered Rate (LIBOR)
Debt
Debt Instrument, Basis Spread on Variable Rate			5.15%
KeyBank National Association \| Equipment Loan
Debt
Debt Instrument, Face Amount	$ 4.7
Debt Instrument, Monthly Installment, Amount	$ 147.0
Number Of Monthly Installments	36 months
Annual percent of premium prepayment	3.00%
Annual premium decline in premium prepayment	1.00%
Debt Instrument, Interest Rate, Stated Percentage	7.45%