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Significant Accounting Policies Segment Information (Details) | Dec. 31, 2011 locations segments divisions
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Segment Reporting Information |
Number of Regional Operating Divisions | 11
Numer of Segments | 1
Number of Office Locations | 10

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- Definition Number of Office Locations + References No definition available. + Details
Name: | htld_NumberOfOfficeLocations
Namespace Prefix: | htld_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Regional Operating Divisions + References No definition available. + Details
Name: | htld_NumberOfRegionalOperatingDivisions
Namespace Prefix: | htld_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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- Definition Numer of Segments + References No definition available. + Details
Name: | htld_NumerOfSegments
Namespace Prefix: | htld_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | instant

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