Note 5 - Leases - Maturities of operating lease liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Weighted average remaining lease term, operating	7 months 6 days
Weighted average remaining lease term, financing	2 years 7 months 6 days
Weighted average discount rate, operating	8.50%
Weighted average discount rate, financing	4.10%
Maturities of financing lease liabilities
2021	$ 731
2022	3,510
2023	3,173
2024	945
Total	7,904
Less: Amounts representing interest	(455)
Present value of lease obligations	8,359
Maturities of operating lease liabilities
2021	16
2022	41
Total	57
Less: Amounts representing interest	(13)
Present value of lease obligations	44
Maturities of lease liabilities
2021	747
2022	3,551
2023	3,173
2024	945
Total	8,416
Less: Amounts representing interest	(468)
Present value of lease obligations	$ 7,948	$ 110

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

No definition available.

Name:	metc_LeaseLiabilities
Namespace Prefix:	metc_
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

Name:	metc_LeaseLiabilityPaymentDueYearThree
Namespace Prefix:	metc_
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 next fiscal year following current fiscal year.

+ References

No definition available.

+ Details

Name:	metc_LeaseLiabilityPaymentsDueNextTwelveMonths
Namespace Prefix:	metc_
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 four 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
Period Type:	instant

- 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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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.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

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

+ References

No definition available.

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Data Type:	xbrli:stringItemType
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- References

No definition available.

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

- 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
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Balance Type:	credit
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- Definition

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

+ References

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Balance Type:	credit
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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

+ Details

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

- Definition

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in fourth 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 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

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

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

+ References

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-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
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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

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- References

No definition available.

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

- Definition

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

+ References

+ Details

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

- 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

+ Details

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- Definition

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

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

- 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.

+ References

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