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Note 1 - Summary of Significant Accounting Policies (Details Textual) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) oz T	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Capitalized Drilling Costs	$ 6,800	$ 6,700	$ 5,300
Foreign Currency Transaction Gain (Loss), Realized	(2,926)	24,551	$ 11,535
Deferred Tax Assets, Net of Valuation Allowance, Current	12,293	$ 17,980
Equity Securities [Member]
Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax	$ 1,800
Silver [Member]
Metals Contained in Concentrates | oz	1,400,000
Gold [Member]
Metals Contained in Concentrates | oz	4,679
Zinc [Member]
Metals Contained in Concentrates | T	10,166
Lead [Member]
Metals Contained in Concentrates | T	4,052
Minimum [Member]
Property, Plant and Equipment, Useful Life	1 year
Maximum [Member]
Property, Plant and Equipment, Useful Life	22 years

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