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		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Coal Workers Pneumoconiosis [Member]
Service Cost	$ 727	$ 1,115	$ 2,179	$ 3,345
Interest Cost	1,265	1,178	3,795	3,533
Amortization of Actuarial Loss	1,059	2,091	3,178	6,273
State Administrative Fees and Insurance Bond Premiums	0	0	0	0
Net Periodic Benefit (Credit) Cost	3,051	4,384	9,152	13,151
Workers Compensation [Member]
Service Cost	1,230	1,059	3,690	3,177
Interest Cost	343	282	1,027	846
Amortization of Actuarial Loss	(106)	(45)	(316)	(135)
State Administrative Fees and Insurance Bond Premiums	449	445	1,334	1,357
Net Periodic Benefit (Credit) Cost	$ 1,916	$ 1,741	$ 5,735	$ 5,245