Bank Debt (Details) (USD $)	12 Months Ended
Dec. 31, 2014 agreement
Debt Instrument [Line Items]
Deferred financing costs expensed	$ 1,000,000us-gaap_DebtInstrumentFeeAmount
Credit agreement, amount outstanding	306,000,000
Leverage ratio	273.00%hnrg_LeverageRatio
Number of interest rate swaps	2
Fair value (liability) of interest rate swaps	(700,000)
Fair value of long term asset	1,700,000
Fair value of current liability	2,400,000
Debt maturity date	Aug. 29, 2019
PNC Bank [Member]
Debt Instrument [Line Items]
Closing costs of debt	6,800,000
Loan initiation amortization period	5 years
Credit facility, maximum borrowing capacity	365,000,000
Maximum [Member]
Debt Instrument [Line Items]
Maximum leverage ratio	325.00%
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	145,000,000
Revolving Credit Facility [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	250,000,000
Term Loan [Member] \| Debt Instrument, Redemption, Period Five [Member]
Debt Instrument [Line Items]
Loan annual amortization	20.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period Four [Member]
Debt Instrument [Line Items]
Loan annual amortization	20.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period One [Member]
Debt Instrument [Line Items]
Loan annual amortization	10.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period Three [Member]
Debt Instrument [Line Items]
Loan annual amortization	15.00%
Term Loan [Member] \| Debt Instrument, Redemption, Period Two [Member]
Debt Instrument [Line Items]
Loan annual amortization	15.00%
Term Loan [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Debt face amount	175,000,000
Term Loan [Member] \| Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit agreement, amount outstanding	161,000,000
Sunrise Coal [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Percentage decrease in amount of debt with maximum interest rate per quarter after commencement date	10.00%
Date that the percentage of debt with a maximum interest rate begins to decrease quarterly	Mar. 31, 2016
Sunrise Coal [Member] \| Maximum [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Interest rate maximum	5.00%
Sunrise Coal [Member] \| Revolving Credit Facility [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Amount of debt with maximum interest rate	100,000,000
Sunrise Coal [Member] \| Term Loan [Member] \| PNC Bank [Member]
Debt Instrument [Line Items]
Amount of debt with maximum interest rate	$ 175,000,000
Leverage Ratio Less Than 1 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	2.25%
Leverage Ratio Between 1 and 1.5 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	2.50%
Leverage Ratio Between 1.5 and 2 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	2.75%
Leverage Ratio Between 2 and 2.5 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	3.00%
Leverage Ratio Above 2.5 [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Debt, interest rate spread on variable rate	3.50%

Amount of debt with maximum interest rate

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Leverage Ratio

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Loan Initiation Amortization Period - Years

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Maximum leverage ratio

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Percentage decrease in amount of debt with maximum interest rate

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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.

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- Definition

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

+ References

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

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

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- Definition

Maximum contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

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

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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- Definition

Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

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Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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Fair value as of the balance sheet date of interest rate derivative assets, net of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized on the balance sheet.

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Amount borrowed under the credit facility as of the balance sheet date.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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- Definition

Number of interest rate derivative instruments held by the entity at the reporting date.

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