Note 23 - Commitments and Contingent Liabilities (Details Textual) $ in Thousands		12 Months Ended
	Aug. 23, 2017	Dec. 31, 2021 USD ($)
Number of Mines Sold		5
Payment Under Guarantees		$ 1,090
Guarantees, Maximum Exposure		1,000
Casey Litigation [Member] | Pending Litigation [Member]
Loss Contingency, Number of Plaintiffs	2
United Mine Workers of America 1992 Benefit Plan Litigation [Member] | Pending Litigation [Member] | Minimum [Member]
Estimated Liability, Annual Servicing Cost, Next Ten Years		10,000
United Mine Workers of America 1992 Benefit Plan Litigation [Member] | Pending Litigation [Member] | Maximum [Member]
Estimated Liability, Annual Servicing Cost, Next Ten Years		$ 20,000