Note 12 - Commitments and Contingent Liabilities (Details Textual) - Pending Litigation [Member] $ in Millions	Aug. 23, 2017	Jun. 30, 2022 USD ($)
Casey Litigation [Member]
Loss Contingency, Number of Plaintiffs	2
United Mine Workers of America 1992 Benefit Plan Litigation [Member] | Minimum [Member]
Estimated Liability, Annual Servicing Cost, Next Ten Years		$ 10
United Mine Workers of America 1992 Benefit Plan Litigation [Member] | Maximum [Member]
Estimated Liability, Annual Servicing Cost, Next Ten Years		$ 20