Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details) - Major Components of Property, Plants, Equipment and Mineral Interests (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, plants, equipment and mineral interests	$ 2,306,972	$ 1,433,195
Less accumulated depreciation, depletion and amortization	515,371	436,536
Net carrying value	1,791,601	996,659
Mining Properties Including Asset Retirement Obligations [Member]
Property, Plant and Equipment [Line Items]
Property, plants, equipment and mineral interests	312,692	294,573
Mine Development [Member]
Property, Plant and Equipment [Line Items]
Property, plants, equipment and mineral interests	204,598	151,504
Plant and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plants, equipment and mineral interests	626,818	419,377
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plants, equipment and mineral interests	15,799	15,788
Mineral Interests [Member]
Property, Plant and Equipment [Line Items]
Property, plants, equipment and mineral interests	946,144	375,028
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plants, equipment and mineral interests	$ 200,921	$ 176,925