Note 5 - Asset Retirement Obligations (Details)	Dec. 31, 2020	Dec. 31, 2019
Measurement Input, Discount Rate [Member]
Asset Retirement Obligation, Measurement Input	0.04	0.04

Value of input used to measure asset retirement obligation.

No definition available.

Name:	metc_AssetRetirementObligationMeasurementInput
Namespace Prefix:	metc_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant