Note 4 - Commitments, Contingencies and Obligations (Details Textual) $ in Millions		1 Months Ended					3 Months Ended			12 Months Ended
	Apr. 12, 2013 USD ($)	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Dec. 31, 2014 USD ($)	Aug. 31, 2012 USD ($)	Jun. 30, 2011 USD ($)	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)	Mar. 05, 2018 USD ($)	Mar. 05, 2018 CAD ($)
Environmental Remediation Expense							$ 570,000	$ 1,262,000
Contractual Obligation, Total							4,300,000
Finance Lease, Liability, Payment, Due, Total							16,185,000
Lessee, Operating Lease, Liability, Payments, Due, Total							22,899,000
Performance Obligation Commitments [Member]
Surety Bonds							185,300,000
Lucky Friday [Member]
Open Purchase Orders							1,500,000
Casa Berardi [Member]
Open Purchase Orders							400,000
Greens Creek [Member]
Open Purchase Orders							3,900,000
Nevada Operations [Member]
Open Purchase Orders							2,900,000
Senior Notes [Member]
Proceeds from Issuance of Debt	$ 500,000,000
Debt Instrument, Increase (Decrease), Net, Total										$ 6,500,000
Debt Instrument, Face Amount	$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage	6.875%
Series 2018-A Senior Notes [Member]
Debt Instrument, Face Amount											$ 30,800,000	$ 40
Debt Instrument, Issuance, Discount Rate											0.58%	0.58%
Debt Instrument, Interest Rate, Stated Percentage											4.68%	4.68%
Canadian Assets of Klondex [Member]
Ownership Percentage			13.00%
Lawsuit in Lincoln County, Montana Courts for Montanore Project [Member]
Surety Bonds							$ 1,100,000
Lawsuit in Lincoln County, Montana Courts for Montanore Project [Member] | Subsidiaries [Member]
Loss Contingency, Damages Awarded, Value		$ 3,325,000
Lawsuit filed in Ontario (Canada) Superior Court of Justice [Member] | Waterton Warrants [Member]
Class of Warrant or Right, Issued During Period, Value			$ 3,700,000
Class of Warrant or Right, Warrants Entitled, Value			8,900,000
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