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v3.21.2

Subsequent Events (Details) $ in Thousands | 9 Months Ended
--- | ---
Sep. 30, 2021 USD ($) shares
Subsequent Events [Abstract] |
Repurchase of Common Stock, Shares | shares | 37,759
Payments for Repurchase of Common Stock | $ | $ 600

X
- Definition Payments for Repurchase of Common Stock1 + References No definition available. + Details
Name: | htld_PaymentsForRepurchaseOfCommonStock1
Namespace Prefix: | htld_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Repurchase of Common Stock, Shares + References No definition available. + Details
Name: | htld_RepurchaseOfCommonStockShares
Namespace Prefix: | htld_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_SubsequentEventsAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration