Note 8 - Leases - Maturities of operating lease liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Weighted average remaining lease term, operating	3 months 18 days
Weighted average remaining lease term, financing	2 years 4 months 24 days
Weighted average discount rate, operating	8.50%
Weighted average discount rate, financing	4.10%
Maturities of financing lease liabilities
2022	$ 3,716
2023	3,452
2024	1,204
Total undiscounted lease payments	8,372
Less: Amounts representing interest	(312)
Present value of lease obligations	8,060	$ 0
Maturities of operating lease liabilities
2022	33
Total undiscounted lease payments	33
Less: Amounts representing interest	(8)
Present value of lease obligations	25	100
Maturities of lease liabilities
2022	3,749
2023	3,452
2024	1,204
Total	8,405
Less: Amounts representing interest	(320)
Present value of lease obligations	$ 8,085	$ 110

Refers to the amount lease liabilities, includes both operating and financing.

No definition available.

Name:	metc_LeaseLiabilities
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payment for lease to be paid in third fiscal year following current fiscal year.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Amount of lessee's undiscounted obligation for lease payment for lease to be paid in next fiscal year following current fiscal year.

+ References

No definition available.

+ Details

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Namespace Prefix:	metc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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- Definition

Amount of lessee's undiscounted obligation for lease payment for lease to be paid in second fiscal year following current fiscal year.

+ References

No definition available.

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for lease.

+ References

No definition available.

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments.

+ References

No definition available.

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- Definition

+ References

No definition available.

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- References

No definition available.

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- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI https://asc.fasb.org/extlink&oid=128292326&loc=SL77918701-209980

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of lessee's undiscounted obligation for lease payments for finance lease.

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for finance lease.

+ References

+ Details

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- Definition

Weighted average discount rate for finance lease calculated at point in time.

+ References

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- Definition

Weighted average remaining lease term for 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/2003/role/disclosureRef
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- References

No definition available.

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease.

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.

+ References

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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

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- Definition

Weighted average discount rate for operating lease calculated at point in time.

+ References

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- Definition

Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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