Consolidated Statement of Operations (Parentheticals) (USD $) In Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
(1) Included in interest expense: credits for the change in the estimated fair value of interest rate swaps.	$ 166	$ 191	$ 354	$ 330

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hnrg_IncludedInInterestExpenseCreditsForTheChangeInTheEstimatedFairValueOfInterestRate

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hnrg

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xbrli:monetaryItemType

Balance Type:

credit

Period Type:

duration