XML 56 R45.htm IDEA: XBRL DOCUMENT
v3.20.2

Significant Accounting Policies Income Taxes (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Significant Accounting Policies [Abstract] |  |
PortionOfTaxBenefitRecordedPositionsMoreLikelyThanNotToBeSustained | 50.00% |
Valuation Allowance Against Any Deferred Tax Asset | $ 0 | $ 0

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

X
- Definition Significant Accounting Policies [Abstract] + References No definition available. + Details
Name: | htld_SignificantAccountingPoliciesAbstract
Namespace Prefix: | htld_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Valuation Allowance Against Any Deferred Tax Asset + References No definition available. + Details
Name: | htld_ValuationAllowanceAgainstAnyDeferredTaxAsset
Namespace Prefix: | htld_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration