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Significant Accounting Policies Self-Insurance Accruals (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2014 | Dec. 31, 2013
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Significant Accounting Policies [Abstract] |  |
Health insurance reserves | $ 6.7 htld_HealthInsuranceReserves | $ 6.1 htld_HealthInsuranceReserves

X
- Definition Self insurance health insurance reserves for estimated cost of health related claims, including estimated expenses incurred but not reported + References No definition available. + Details
Name: | htld_HealthInsuranceReserves
Namespace Prefix: | htld_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
Name: | htld_SignificantAccountingPoliciesAbstract
Namespace Prefix: | htld_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration