Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details) [Line Items]
Total Capital Expenditures	$ 137.4
Accumulated Capitalized Interest Costs	13.5	$ 11.8
Capital Leased Assets, Gross	39.9	39.5
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	24.4	15.3
Operating Leases, Rent Expense	3.8	$ 3.5	$ 3.1
Lucky Friday [Member]
Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details) [Line Items]
Total Capital Expenditures	53.3
Greens Creek [Member]
Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details) [Line Items]
Total Capital Expenditures	43.4
Casa Berardi [Member]
Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details) [Line Items]
Total Capital Expenditures	35.5
San Sebastian Unit [Member]
Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details) [Line Items]
Total Capital Expenditures	$ 3.4