Note 10 - Revenue - Domestic Revenues an Export Revenues (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
REVENUES
Revenues	$ 45,612	$ 61,380	$ 65,761	$ 57,460	$ 44,187	$ 62,166	$ 65,278	$ 55,943	$ 230,213	$ 227,574	$ 61,036
Domestic Coal Revenues
REVENUES
Revenues									164,256	121,433	31,199
Export Coal Revenues
REVENUES
Revenues									$ 65,957	$ 106,141	27,599
Coal Processing
REVENUES
Revenues											$ 2,238