XML 41 R30.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Basis of Presentation Increase to Cash Flow from Investing Abstract (Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Increase to Cash from Investing Activity [Abstract] |  |
ASU 2016-18 Reclassification Adjustment | $ (5.9) | $ 3.6

X
- Definition Increase to Cash from Investing Activity [Abstract] + References No definition available. + Details
Name: | htld_IncreasetoCashfromInvestingActivityAbstract
Namespace Prefix: | htld_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of a reclassification adjustment made to prior period financial statement amounts. + References No definition available. + Details
Name: | us-gaap_PriorPeriodReclassificationAdjustment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration