Note 5 - Asset Retirement Obligations (Details) - Measurement Input, Discount Rate [Member]	Dec. 31, 2021	Dec. 31, 2020
Asset Retirement Obligation, Measurement Input	0.04	0.04
Asset Retirement Obligation inflation adjustment, Measurement input	2.30%	2.00%

Value of input used to measure asset retirement obligation, inflation adjustment.

No definition available.

Name:	metc_AssetRetirementObligationMeasurementInputInflationAdjustment
Namespace Prefix:	metc_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant