Accrued reclamation and closure costs total.

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Amount of increase (decrease) in the asset retirement obligation before discounting the costs to present value from changes in the amount associated with the settlement of the obligation.

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Amount of reclamation liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of assets related to reclamation insurance expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date

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The inflation rate uses to valuing asset retirement obligations asset and liability.

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Debt to the entity for remediation at the site.

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Percentage of ownership in properties.

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Amount of asset retirement obligations incurred during the period.

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Risk-free interest rate assumption used in valuing an instrument.

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Amount of cash outflow reducing loss contingency liability.

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Amount of cash inflow for proceeds from settlement of insurance claim, classified as investing activities. Excludes insurance settlement classified as operating activities.

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Note 4 - Environmental and Reclamation Activities (Details Textual) - USD ($)		1 Months Ended	3 Months Ended			12 Months Ended
	Nov. 07, 2016	Aug. 31, 2016	Dec. 31, 2017	Sep. 30, 2016	Jun. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 15, 2015	Dec. 31, 2014
Proceeds from Insurance Settlement, Investing Activities						$ 7,745,000
Accrued Reclamation and Closure Costs Total			$ 86,045,000			$ 86,045,000	$ 85,580,000	$ 95,538,000		$ 57,250,000
Asset Retirement Obligation [Member]
Fair Value Assumptions, Risk Free Interest Rate						5.75%
Minimum [Member]
Inflation Rate, Asset Retirement Obligation						2.00%
Minimum [Member] \| Reclamation and Abandonment Costs [Member]
Fair Value Assumptions, Risk Free Interest Rate						5.75%
Maximum [Member]
Inflation Rate, Asset Retirement Obligation						4.00%
Maximum [Member] \| Reclamation and Abandonment Costs [Member]
Fair Value Assumptions, Risk Free Interest Rate						14.50%
Nelson Tunnel/Commodore Site [Member] \| United States and Colorado [Member]
Loss Contingency Accrual, Payments		$ 6,000,000
Gilt Edge Mine Superfund Site [Member] \| United States and South Dakota [Member]
Loss Contingency Accrual, Payments	$ 3,900,000
Gilt Edge Mine Superfund Site [Member] \| United States, South Dakota, Insurers and Another Potentially Responsible Party [Member]
Loss Contingency Accrual, Payments	$ 6,700,000
Gilt Edge Site and Nelson Tunnel/Commodore Site [Member]
Liability for Remediation					$ 9,900,000
San Sebastian [Member]
Asset Retirement Obligation, Revision of Estimate Before Discounting						$ 0.50
Asset Retirement Obligation, Liabilities Incurred			1,200,000
Casa Berardi [Member]
Asset Retirement Obligation, Revision of Estimate Before Discounting			1,000,000
Asset Retirement Obligation, Liabilities Incurred			$ 700,000
Revett Mining Company, Inc. [Member]
Ownership Percentage									100.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Reclamation Liability					17,500,000				$ 17,513,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Reclamation Insurance Asset					$ 16,800,000				$ 16,800,000
Proceeds from Insurance Settlement, Investing Activities				$ 16,000,000
Revett Mining Company, Inc. [Member] \| Mining Properties and Mineral Rights [Member]
Ownership Percentage					100.00%