XML 81 R50.htm IDEA: XBRL DOCUMENT
v3.20.4

Note 6 - Income Taxes - Changes in the Valuation Allowance (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Balance at beginning of year | $ (86,634) | $ (94,981) | $ (78,684)
Balance at end of year | (77,210) | (86,634) | (94,981)
Increase Due to Uncertainty of Recovery [Member] |  |  |
Valuation allowance, deferred tax asset, increase (decrease) | 786 | 686 | (5,700)
Decrease Related to Utilization and Expiration [Member] |  |  |
Valuation allowance, deferred tax asset, increase (decrease) | 8,638 | 1,756 | 873
Klondex Mines Ltd [Member] | Business Acquisition [Member] |  |  |
Valuation allowance, deferred tax asset, increase (decrease) | $ 0 | $ 5,905 | $ (11,470)

X
- 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/disclosureRef -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
Name: | us-gaap_DeferredTaxAssetsValuationAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319 + Details
Name: | us-gaap_ValuationAllowanceDeferredTaxAssetChangeInAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

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

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=hl_KlondexMinesLtdMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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