Note 4 - Bank Debt - Maximum Leverage Ratio (Details)	Mar. 31, 2023
Credit Agreement [Member]
Maximum Leverage Ratio	2.25

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