Note 8 - Revenue - Domestic Revenues an Export Revenues (Details) $ in Thousands, T in Millions	3 Months Ended
	Mar. 31, 2022 USD ($) T $ / T	Mar. 31, 2021 USD ($)
REVENUES
Revenues	$ 154,882	$ 43,455
Term of domestic sales contracts	1 year
Domestic Coal Revenues
REVENUES
Revenues	$ 60,094	20,107
Export Revenues
REVENUES
Revenues	$ 94,788	$ 23,348
Fixed Priced Contracts
REVENUES
Outstanding performance obligation, mass | T	1.5
Average per ton | $ / T	188
Contracts with Indexed Based Pricing Mechanisms
REVENUES
Outstanding performance obligation, mass | T	0.2