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Note 5 - Bank Debt - Maximum Leverage Ratio (Details) - Credit Agreement [Member] | Dec. 31, 2021
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Periods Ended March 31, 2021 and June 30, 2021 [Member] |
Maximum Leverage Ratio | 3.00
Period Ended March 31, 2022 and Thereafter [Member] |
Maximum Leverage Ratio | 2.50

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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
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Namespace Prefix: | hnrg_
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Balance Type: | na
Period Type: | instant

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- Details
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- Details
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Data Type: | na
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- Details
Name: | srt_StatementScenarioAxis=hnrg_PeriodEndedMarch312022AndThereafterMember
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Data Type: | na
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