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Note 5 - Income Taxes - Changes in the Valuation Allowance (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Balance at beginning of year | $ (99,602) | $ (115,806) | $ (32,094)
Balance at end of year | (78,684) | (99,602) | (115,806)
Increase Due to Uncertainty of Recovery [Member] |  |  |
Valuation allowance, deferred tax asset, increase (decrease) | (14,964) | (2,868) | (92,393)
Decrease Related to Utilization and Expiration [Member] |  |  |
Valuation allowance, deferred tax asset, increase (decrease) | $ 35,882 | $ 19,072 | $ 8,681

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- Definition Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 45 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=84176650&loc=d3e32123-109318 + Details
Name: | us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_ValuationAllowanceByDeferredTaxAssetAxis=hl_DecreaseRelatedToUtilizationAndExpirationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |