Note 2 - Summary of Significant Accounting Policies - Financial Instruments (Details) $ in Millions	Jun. 30, 2022 USD ($)
Summary of Significant Accounting Policies.
Excess fair value of debt over carrying value	$ 3.1

The amount that the fair value of debt exceeds the carrying value at balance sheet date.

No definition available.

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