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Note 12 - Business Segments, Sales of Products and Significant Customers - Percentage of Sales by Segments (Details) - Revenue Benchmark [Member] | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Percentage of sales | 100.00% | 100.00% | 100.00%
Greens Creek [Member] |  |  |
Percentage of sales | 47.40% | 44.50% | 46.70%
Lucky Friday [Member] |  |  |
Percentage of sales | 9.10% | 2.50% | 1.80%
Casa Berardi [Member] |  |  |
Percentage of sales | 30.20% | 28.70% | 37.10%
San Sebastian [Member] |  |  |
Percentage of sales | 4.80% | 8.30% | 8.90%
Nevada Operations [Member] |  |  |
Percentage of sales | 8.50% | 16.00% | 5.50%

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