XML 71 R54.htm IDEA: XBRL DOCUMENT
v3.22.1

Note 15 - Subsequent Events (Details Textual) - Senior Unsecured Convertible Notes [Member] - Subsequent Event [Member] - USD ($) $ in Millions | May 20, 2022 | May 02, 2022
--- | --- | ---
Four Board Members [Member] |  |
Proceeds from Issuance of Unsecured Debt |  | $ 5
Three Board Members and One Unrelated Party [Member] |  |
Proceeds from Issuance of Unsecured Debt | $ 5 |

X
- Definition The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromIssuanceOfUnsecuredDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=hnrg_SeniorUnsecuredConvertibleNotesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CounterpartyNameAxis=hnrg_FourBoardMembersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CounterpartyNameAxis=hnrg_ThreeBoardMembersAndOneUnrelatedPartyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |