Note 4 - Commitments, Contingencies and Obligations (Details Textual) - USD ($) $ in Thousands		1 Months Ended					3 Months Ended
	Oct. 30, 2019	Oct. 31, 2019	Jul. 31, 2018	Dec. 31, 2014	Aug. 31, 2012	Jun. 30, 2011	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2014	Feb. 19, 2020	Dec. 31, 2019
Environmental Remediation Expense		$ 6,100					$ 516	$ 570
Contractual Obligation, Total							2,300
Finance Lease, Liability, Payment, Due, Total							11,861
Lessee, Operating Lease, Liability, to be Paid, Total							16,082
Performance Obligation Commitments [Member]
Surety Bonds							181,300
Letters of Credit Outstanding, Amount							28,700
Lucky Friday [Member]
Open Purchase Orders							2,300
Casa Berardi [Member]
Open Purchase Orders							600
Greens Creek [Member]
Open Purchase Orders							3,300
Nevada Operations [Member]
Open Purchase Orders							600
Senior Notes [Member] | The 2028 Senior Notes [Member]
Debt Instrument, Face Amount										$ 475,000
Debt Instrument, Interest Rate, Stated Percentage										7.25%
Long-term Debt, Gross							$ 475,000
Senior Notes [Member] | The 2021 Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage											6.875%
Long-term Debt, Gross											$ 506,500
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									$ 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