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Equity Investment in Sunrise Energy (Narrative) (Details) | Dec. 31, 2015
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Sunrise Energy [Member] |
Equity method investment ownership percentage | 50.00%

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- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
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Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | dei_LegalEntityAxis=hnrg_SunriseEnergyMember
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Data Type: | na
Balance Type: |
Period Type: |