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Note 16 - Organizational Restructuring (Details Textual) $ in Millions | Jun. 30, 2024 USD ($) | Mar. 31, 2024 USD ($) | Feb. 23, 2024
--- | --- | --- | ---
Number Of Employees |  |  | 110
Percentage of Workforce |  |  | 12.00%
Restructuring Reserve | $ 0.8 | $ 1.1 |
Operating Expenses [Member] |  |  |
Restructuring Reserve | $ 1.9 |  |

X
- Definition The number of employees in the workforce reduction. + References No definition available. + Details
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Namespace Prefix: | hnrg_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition The percentage of the workforce Reduction. + References No definition available. + Details
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Namespace Prefix: | hnrg_
Data Type: | dtr-types:percentItemType
Balance Type: | na
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- Definition Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 420 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 2 -Subparagraph (SAB Topic 5.P.4.b.2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479823/420-10-S99-2 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 420 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 1 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org/1943274/2147482017/420-10-50-1 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |