Note 8 - Revenue - Domestic Revenues an Export Revenues (Details) $ in Thousands, T in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) T $ / T	Mar. 31, 2022 USD ($)
REVENUES
Revenues	$ 166,360	$ 154,882
Term of domestic sales contracts	1 year
Domestic Coal Revenues
REVENUES
Revenues	$ 40,027	60,094
Export Revenues
REVENUES
Revenues	$ 126,333	$ 94,788
Fixed Priced Contracts
REVENUES
Outstanding performance obligation, mass | T	1.9
Average per ton | $ / T	197
Contracts with Indexed Based Pricing Mechanisms
REVENUES
Outstanding performance obligation, mass | T	0.8