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Note 12 - Fair Value Measurements (Details Textual) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Cash and Cash Equivalents, Restricted Cash Balances, Deposits	$ 10.7	$ 7.1

X

- Definition

The cash equivalents and restricted cash related to deposits.

+ References

No definition available.

+ Details

Name:	hnrg_CashAndCashEquivalentsRestrictedCashBalancesDeposits
Namespace Prefix:	hnrg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant