Amount of debt with maximum interest rate

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Debt service coverage ratio

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Leverage Ratio

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Liquidity

+ References

No definition available.

+ Details

Name:	hnrg_Liquidity
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The net increase(decrease) in interest income during the period representing the allocation of deferred loan origination fees less deferred loan origination costs using the effective interest method over the term of the debt arrangement to which they pertain taking into account the effect of prepayments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the fee that accompanies borrowing money under the debt instrument.

+ References

+ Details

Name:	us-gaap_DebtInstrumentFeeAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value of the amount outstanding under the credit facility.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

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Balance Type:
Period Type:

- Details

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Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=hnrg_TermLoanMember
Namespace Prefix:
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Bank Debt (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Bank Debt (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	May 21, 2018
Debt Instrument [Line Items]
Leverage ratio	212.00%
Debt service coverage ratio	229.00%
Interest rate effective percentage	6.51%
Credit Agreement [Member]
Debt Instrument [Line Items]
Closing costs of debt	$ 8.8
Deferred financing costs expensed	6.9	$ 7.4
Credit agreement, amount outstanding	168.0
Borrowing capacity	77.0
Liquidity	$ 88.0
Debt, interest rate spread on variable rate	4.00%
Interest rate effective percentage	6.00%
Minimum [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt service coverage ratio	125.00%
London Interbank Offered Rate (LIBOR) [Member] \| Minimum [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	3.00%
London Interbank Offered Rate (LIBOR) [Member] \| Maximum [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	4.50%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Amount of debt with maximum interest rate	$ 53.0
Revolving Credit Facility [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	$ 43.0		$ 120.0
Debt maturity date	May 21, 2022
Term Loan [Member] \| Credit Agreement [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	$ 125.0