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Note 1 - Basis of Preparation of Financial Statements (Details Textual) $ in Millions | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 | Sep. 30, 2021 USD ($) | Dec. 31, 2020 USD ($) oz
Casa Berardi [Member] |  |  |
Decrease in Expected Gold Production Due to Suspension (Ounce) | oz |  |  | 11,700
Suspension Costs |  |  | $ 1.6
Pandemic Related Procedures Costs |  | $ 1.9 |
San Sebastian [Member] |  |  |
Suspension Costs |  |  | 1.8
Greens Creek [Member] |  |  |
Suspension Costs from Quarantining Employee Per Week |  | $ 1.0 | $ 2.3
Percentage of Increase (Decrease) in Silver Production | (30.00%) |  |

X
- Definition The amount of decrease in the expected gold production due to suspension orders. + References No definition available. + Details
Name: | hl_DecreaseInExpectedGoldProductionDueToSuspension
Namespace Prefix: | hl_
Data Type: | dtr-types:massItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of costs related to the COVID-19 pandemic procedures. + References No definition available. + Details
Name: | hl_PandemicRelatedProceduresCosts
Namespace Prefix: | hl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The percentage of increase (decrease) in silver production from comparative period. + References No definition available. + Details
Name: | hl_PercentageOfIncreaseDecreaseInSilverProduction
Namespace Prefix: | hl_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of suspension costs during the period. + References No definition available. + Details
Name: | hl_SuspensionCosts
Namespace Prefix: | hl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of costs incurred per week from the employee quarantine. + References No definition available. + Details
Name: | hl_SuspensionCostsFromQuarantiningEmployeePerWeek
Namespace Prefix: | hl_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=hl_CasaBerardiMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=hl_SanSebastianMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=hl_GreensCreekMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |