XML 47 R36.htm IDEA: XBRL DOCUMENT
v3.20.2

Significant Accounting Policies Trade Receivables and Allowance for Doubtful Accounts (Details) $ in Millions | Dec. 31, 2019 USD ($) d | Dec. 31, 2018 USD ($)
--- | --- | ---
Significant Accounting Policies [Abstract] |  |
Customer credit terms (in days) | d | 30 |
Allowance for Doubtful Accounts Receivable, Current | $ | $ 1.1 | $ 0.9

X
- Definition customer credit terms days + References No definition available. + Details
Name: | htld_CustomerCreditTermsDays
Namespace Prefix: | htld_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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 Amount of allowance for credit loss on accounts receivable, classified as current. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(4) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5074-111524 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=118955202&loc=SL82895884-210446 + Details
Name: | us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant