Current and Long-Term Financing (Debt Schedule) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
Current portion of borrowings outstanding	$ 3,953	$ 3,649
Long-term portion of borrowings outstanding	22,003	16,019
NACoal
Debt Instrument [Line Items]
Revolving credit agreement		0
Other debt	25,956	19,668
Total debt outstanding	35,956	19,668
Current portion of borrowings outstanding	13,953	3,649
Long-term portion of borrowings outstanding	22,003	16,019
Total available borrowings, net of limitations, under revolving credit agreement	115,120	116,285
Unused revolving credit agreement	$ 105,120	$ 116,285
Weighted average stated interest rate on total borrowings	6.60%	3.90%