Note 5 - Commitments, Contingencies and Obligations (Details Textual) $ in Millions		1 Months Ended			3 Months Ended			9 Months Ended		12 Months Ended	28 Months Ended
	Apr. 12, 2013 USD ($)	Jul. 31, 2018 USD ($)	Aug. 31, 2012 USD ($)	Jun. 30, 2011 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)	Mar. 05, 2018 USD ($)	Mar. 05, 2018 CAD ($)
Environmental Remediation Expense					$ 1,852,000	$ 2,940,000		$ 4,534,000	$ 5,044,000
Contractual Obligation, Total					1,600,000			1,600,000
Capital Leases, Future Minimum Payments Due, Total					15,675,000			15,675,000
Surety Bonds					181,600,000			181,600,000
Lucky Friday [Member]
Open Purchase Orders					400,000			400,000
Casa Berardi [Member]
Open Purchase Orders					2,000,000			2,000,000
Greens Creek [Member]
Open Purchase Orders					14,200,000			14,200,000
Nevada Operations [Member]
Open Purchase Orders					$ 5,300,000			5,300,000
Senior Notes [Member]
Proceeds from Issuance of Debt	$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.875%
Debt Instrument, Increase (Decrease), Net, Total										$ 6,500,000
Debt Instrument, Face Amount	$ 500,000,000
Series 2018-A Senior Notes [Member]
Debt Instrument, Interest Rate, Stated Percentage												4.68%	4.68%
Debt Instrument, Face Amount												$ 30,800,000	$ 40
Debt Instrument, Issuance, Discount Rate												0.58%	0.58%
Waterton Warrants [Member] | Lawsuit filed in Ontario (Canada) Superior Court of Justice [Member]
Class of Warrant or Right, Issued During Period, Value								3,700,000
Class of Warrant or Right, Warrants Entitled, Value								$ 8,900,000
Canadian Assets of Klondex [Member]
Ownership Percentage					13.00%			13.00%
Johnny M Mine Area near San Mateo, New Mexico [Member]
Payment Of Response Costs			$ 1,100,000								$ 1,100,000
Estimated Response Costs		$ 9,600,000						$ 5,600,000
Environmental Remediation Expense							$ 5,600,000
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								$ 221,000,000
Carpenter Snow Creek Superfund Site, Cascade County, Montana [Member]
Estimated Response Costs				$ 4,500,000
Estimated Future Response Cost				$ 100,000,000
Joint Venture [Member] | Rio Grande Silver Inc and Emerald Mining and Leasing LLC [Member]
Equity Method Investment, Ownership Percentage					70.00%			70.00%
Maximum Environmental Remediation Obligation					$ 2,500,000			$ 2,500,000