Note 15 - Properties, Plants, Equipment and Mine Development, net, and Lease Commitments - Major Components of Property, Plants, Equipment and mine development (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Financing Receivable, Past Due [Line Items]
Property, Plant and Equipment	$ 5,007,831	$ 4,704,126
Less accumulated depreciation, depletion and amortization	2,167,004	2,010,007
Net carrying value	2,840,827	2,694,119
Mining properties, including asset retirement obligations
Financing Receivable, Past Due [Line Items]
Property, Plant and Equipment	1,080,946	958,858
Development costs
Financing Receivable, Past Due [Line Items]
Property, Plant and Equipment	719,186	671,741
Plants and equipment
Financing Receivable, Past Due [Line Items]
Property, Plant and Equipment	1,879,231	1,805,236
Land
Financing Receivable, Past Due [Line Items]
Property, Plant and Equipment	32,962	35,680
Mineral interests
Financing Receivable, Past Due [Line Items]
Property, Plant and Equipment	1,150,514	1,166,045
Construction in progress
Financing Receivable, Past Due [Line Items]
Property, Plant and Equipment	$ 144,992	$ 66,566