Note 5 - Bank Debt - Maximum Leverage Ratio (Details) - Credit Agreement [Member]	Dec. 31, 2022
Maximum Leverage Ratio	2.25
Period Ending June 30, 2022 [Member]
Maximum Leverage Ratio	2.50

The maximum leverage ratio (consolidated funded debt / trailing twelve months adjusted EBITDA) under the covenant of the debt instrument.

No definition available.

Name:	hnrg_DebtInstrumentCovenantMaximumLeverageRatio
Namespace Prefix:	hnrg_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant