Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments - Major Components of Property, Plants, Equipment and Mineral Interests (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, plant and equipment, gross	$ 3,734,094	$ 3,634,861
Less accumulated depreciation, depletion and amortization	1,310,396	1,114,857
Net carrying value	2,423,698	2,520,004
Mining Properties Including Asset Retirement Obligations [Member]
Property, plant and equipment, gross	762,355	533,631
Mine Development [Member]
Property, plant and equipment, gross	503,111	444,229
Plant and Equipment [Member]
Property, plant and equipment, gross	1,056,512	988,285
Land [Member]
Property, plant and equipment, gross	32,909	32,953
Mineral Interests [Member]
Property, plant and equipment, gross	1,018,380	1,269,956
Construction in Progress [Member]
Property, plant and equipment, gross	$ 360,827	$ 365,807

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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