Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Payments to Acquire Property, Plant, and Equipment	$ 98,038	$ 164,788	$ 137,443
Accumulated Capitalized Interest Costs	900	16,200
Capital Leased Assets, Gross	48,600	42,200
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	33,100	26,000
Operating Leases, Rent Expense	4,800	$ 4,800	$ 3,800
Lucky Friday [Member]
Payments to Acquire Property, Plant, and Equipment	4,500
Greens Creek [Member]
Payments to Acquire Property, Plant, and Equipment	34,200
Casa Berardi [Member]
Payments to Acquire Property, Plant, and Equipment	47,100
San Sebastian [Member]
Payments to Acquire Property, Plant, and Equipment	$ 11,200