Note 3 - Properties, Plants, Equipment and Mineral Interests, and Lease Commitments (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Payments to Acquire Property, Plant, and Equipment, Total	$ 121,421	$ 136,933	$ 98,038
Accumulated Capitalized Interest Costs	0	0	$ 900
Capital Leased Assets, Gross, Total	64,900	58,400
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation	44,300	$ 38,400
Lucky Friday [Member]
Payments to Acquire Property, Plant, and Equipment, Total	8,900
Greens Creek [Member]
Payments to Acquire Property, Plant, and Equipment, Total	29,300
Mining Assets, Value Beyond Proven and Probable Reserves (VBPP)	181,400
Casa Berardi [Member]
Payments to Acquire Property, Plant, and Equipment, Total	36,100
Mining Assets, Value Beyond Proven and Probable Reserves (VBPP)	321,100
San Sebastian [Member]
Payments to Acquire Property, Plant, and Equipment, Total	5,000
Nevada Operations [Member]
Payments to Acquire Property, Plant, and Equipment, Total	42,100
Mining Assets, Value Beyond Proven and Probable Reserves (VBPP)	$ 382,200