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Significant Accounting Policies Income Taxes (Details) | 12 Months Ended
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Dec. 31, 2012
Income Tax Contingency |
PortionOfTaxBenefitRecordedPositionsMoreLikelyThanNotToBeSustained | 50.00%

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- Definition PortionOfTaxBenefitRecordedPositionsMoreLikelyThanNotToBeSustained + References No definition available. + Details
Name: | htld_Portionoftaxbenefitrecordedpositionsmorelikelythannottobesustained
Namespace Prefix: | htld_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_IncomeTaxContingencyLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration