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v2.4.1.9

Equity Investment in Savoy (Carrying Value and Average Wellhead Prices) (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2014
Reserve Quantities [Line Items] |  |  |
Beginning of year | $ 90,800 us-gaap_CrudeOilAndNaturalGasLiquids | $ 35,300 us-gaap_CrudeOilAndNaturalGasLiquids |
Sales, net of production costs | (11,000)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts | (12,600)us-gaap_SalesAndTransfersOfOilAndGasProducedNetOfProductionCosts |
Net changes in prices and production costs | (5,700)us-gaap_NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts | 1,600 us-gaap_NetIncreaseDecreaseInSalesAndTransferPricesAndProductionCosts |
Extensions and discoveries | 13,300 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts | 57,200 us-gaap_ExtensionsDiscoveriesAdditionsAndImprovedRecoveryLessRelatedCosts |
Revisions of previous quantity estimates | (61,000)us-gaap_RevisionsOfPreviousQuantityEstimates | 2,100 us-gaap_RevisionsOfPreviousQuantityEstimates |
Change in production timing and other | 3,100 us-gaap_IncreaseDecreaseInEstimatedFutureDevelopmentCosts | 3,700 us-gaap_IncreaseDecreaseInEstimatedFutureDevelopmentCosts |
Change in ownership from 45% to 40% | (4,500)us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowOfProvedOilAndGasReservesOther |  |
Accretion of discount | 9,100 us-gaap_AccretionOfDiscount | 3,500 us-gaap_AccretionOfDiscount |
End of year | $ 34,100 us-gaap_CrudeOilAndNaturalGasLiquids | $ 90,800 us-gaap_CrudeOilAndNaturalGasLiquids |
Savoy [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Equity method investment ownership percentage | 40.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / dei_LegalEntityAxis = hnrg_SavoyMember |  | 45.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / dei_LegalEntityAxis = hnrg_SavoyMember
NYMEX Strip Prices [Member] | Oil [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Average wellhead prices | 59 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember / hnrg_UnderlyingBasisAxis = hnrg_NymexStripPricesMember |  |
NYMEX Strip Prices [Member] | Natural Gas Liquids [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Average wellhead prices | 28 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember / hnrg_UnderlyingBasisAxis = hnrg_NymexStripPricesMember |  |
NYMEX Strip Prices [Member] | Natural Gas [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Average wellhead prices | 3.94 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember / hnrg_UnderlyingBasisAxis = hnrg_NymexStripPricesMember |  |
SEC Average Prices [Member] | Oil [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Average wellhead prices | 89 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember / hnrg_UnderlyingBasisAxis = hnrg_SecAveragePricesMember | 95 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_OilReservesMember / hnrg_UnderlyingBasisAxis = hnrg_SecAveragePricesMember |
SEC Average Prices [Member] | Natural Gas Liquids [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Average wellhead prices | 41 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember / hnrg_UnderlyingBasisAxis = hnrg_SecAveragePricesMember | 42 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasLiquidsReservesMember / hnrg_UnderlyingBasisAxis = hnrg_SecAveragePricesMember |
SEC Average Prices [Member] | Natural Gas [Member] |  |  |
Reserve Quantities [Line Items] |  |  |
Average wellhead prices | 4.27 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember / hnrg_UnderlyingBasisAxis = hnrg_SecAveragePricesMember | 3.04 us-gaap_AverageSalesPrices / us-gaap_ReserveQuantitiesByTypeOfReserveAxis = us-gaap_NaturalGasReservesMember / hnrg_UnderlyingBasisAxis = hnrg_SecAveragePricesMember |

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