Note 11 - Business Segments, Sales of Products and Significant Customers - Percentage of Sales by Segments (Details) - Revenue Benchmark [Member]	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Percentage of sales	100.00%	100.00%	100.00%
Greens Creek [Member]
Percentage of sales	44.50%	46.70%	48.10%
Lucky Friday [Member]
Percentage of sales	2.50%	1.80%	3.80%
Casa Berardi [Member]
Percentage of sales	28.70%	37.10%	33.30%
San Sebastian [Member]
Percentage of sales	8.30%	8.90%	14.80%
Nevada Operations [Member]
Percentage of sales	16.00%	5.50%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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