Note 8 - Commitments, Contingencies, and Obligations (Details Textual) - USD ($) $ in Thousands		1 Months Ended					3 Months Ended	12 Months Ended
	Oct. 30, 2019	Oct. 31, 2019	Jul. 31, 2018	Dec. 31, 2014	Aug. 31, 2012	Jun. 30, 2011	Dec. 31, 2014	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Environmental Remediation Expense								$ 3,929	$ 4,690	$ 6,119
Contractual Obligation, Total								100
Finance Lease, Liability, Payment, Due, Total								16,819
Lessee, Operating Lease, Liability, to be Paid, Total								12,622
Performance Obligation Commitments [Member]
Surety Bonds								183,000
Letters of Credit Outstanding, Amount								20,300
Lucky Friday [Member]
Open Purchase Orders								4,200
Casa Berardi [Member]
Open Purchase Orders								700
Greens Creek [Member]
Open Purchase Orders								2,000
Nevada Operations [Member]
Open Purchase Orders								$ 500
Canadian Assets of Klondex [Member]
Ownership Percentage			13.00%
PRP Lawsuit in Mineral County, Colorado [Member]
Loss Contingency, Damages Sought, Value	$ 5,000
Lawsuit filed in Ontario (Canada) Superior Court of Justice [Member] | Waterton Warrants [Member]
Class of Warrant or Right, Issued During Period, Value			$ 3,700
Class of Warrant or Right, Warrants Entitled, Value			8,900
Johnny M Mine Area near San Mateo, New Mexico [Member]
Payment Of Response Costs				$ 1,100	$ 1,100
Estimated Response Costs			$ 9,600				$ 6,100
Environmental Remediation Expense		$ 6,100					$ 5,600
Johnny M Mine Area near San Mateo, New Mexico [Member] | Minimum [Member]
Estimated Alternative Response Costs				0
Johnny M Mine Area near San Mateo, New Mexico [Member] | Maximum [Member]
Estimated Alternative Response Costs				$ 221,000
Carpenter Snow Creek Superfund Site, Cascade County, Montana [Member]
Estimated Response Costs						$ 4,500
Estimated Future Response Cost						$ 100,000