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v3.23.1

Note 4 - Bank Debt - Maximum Leverage Ratio (Details) | Mar. 31, 2023
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Credit Agreement [Member] |
Maximum Leverage Ratio | 2.25

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- Definition The maximum leverage ratio (consolidated funded debt / trailing twelve months adjusted EBITDA) under the covenant of the debt instrument. + References No definition available. + Details
Name: | hnrg_DebtInstrumentCovenantMaximumLeverageRatio
Namespace Prefix: | hnrg_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_DebtInstrumentAxis=hnrg_CreditAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |