Note 4 - Components of Coal Workers' Pneumoconiosis (CWP) and Workers' Compensation Net Periodic Benefit Costs - Components of Net Period Benefit Costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Coal Workers Pneumoconiosis [Member]
Service Cost	$ 726	$ 1,115	$ 1,452	$ 2,230
Interest Cost	1,265	1,177	2,530	2,355
Amortization of Actuarial Loss	1,059	2,091	2,119	4,182
State Administrative Fees and Insurance Bond Premiums	0	0	0	0
Net Periodic Benefit (Credit) Cost	3,050	4,383	6,101	8,767
Workers Compensation [Member]
Service Cost	1,230	1,059	2,460	2,118
Interest Cost	342	282	684	564
Amortization of Actuarial Loss	(105)	(45)	(210)	(90)
State Administrative Fees and Insurance Bond Premiums	448	444	885	912
Net Periodic Benefit (Credit) Cost	$ 1,915	$ 1,740	$ 3,819	$ 3,504