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Note 4 - Commitments, Contingencies and Obligations (Details Textual) $ in Millions		1 Months Ended						3 Months Ended			9 Months Ended		12 Months Ended
	Apr. 12, 2013 USD ($)	Oct. 31, 2019 USD ($)	Oct. 31, 2018 USD ($)	Jul. 31, 2018 USD ($)	Dec. 31, 2014 USD ($)	Aug. 31, 2012 USD ($)	Jun. 30, 2011 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2014 USD ($)	Mar. 05, 2018 USD ($)	Mar. 05, 2018 CAD ($)
Environmental Remediation Expense								$ 1,907,000	$ 1,852,000		$ 3,529,000	$ 4,534,000
Contractual Obligation, Total								1,300,000			1,300,000
Finance Lease, Liability, Payment, Due, Total								15,243,000			15,243,000
Lessee, Operating Lease, Liability, Payments, Due, Total								17,393,000			17,393,000
Letters of Credit Outstanding, Amount								38,500,000			38,500,000
Performance Obligation Commitments [Member]
Surety Bonds								191,800,000			191,800,000
Letters of Credit Outstanding, Amount								38,500,000			38,500,000
Lucky Friday [Member]
Open Purchase Orders								1,800,000			1,800,000
Casa Berardi [Member]
Open Purchase Orders								1,400,000			1,400,000
Greens Creek [Member]
Open Purchase Orders								4,300,000			4,300,000
Nevada Operations [Member]
Open Purchase Orders								500,000			500,000
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			$ 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	5,900,000
Environmental Remediation Expense										$ 5,600,000
Johnny M Mine Area near San Mateo, New Mexico [Member] | Subsequent Event [Member]
Environmental Remediation Expense		$ 5,900,000
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

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