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v3.20.4

Subsequent Events (Details) shares in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2020 USD ($) shares
Subsequent Event [Line Items] |
Repurchase of Common Stock, Shares | shares | 700
Payments For Repurchase Of Common Stock | $ | $ 12,900

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- 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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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration