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Note 11 - Business Segments and Significant Customers - Percentage of Sales by Segments (Details) - Sales Revenue, Net [Member]
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Percentage of sales 100.00% 100.00% 100.00%
Greens Creek [Member]      
Percentage of sales 48.20% 40.30% 51.40%
Lucky Friday [Member]      
Percentage of sales 3.80% 14.70% 14.90%
Casa Berardi [Member]      
Percentage of sales 33.30% 27.40% 33.70%
San Sebastian [Member]      
Percentage of sales 14.80% 17.60%