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| 0000799233-19-000006-index.html | 2019-02-21 16:03:02 | |
| 0000799233-19-000006.txt | 2019-02-21 16:03:02 | |
 0000799233-19-000006-xbrl.zip | 319719 | 2019-02-21 16:03:02 |
| exhibit212018q4.htm | 7175 | 2019-02-21 16:03:02 |
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| exhibit3122018q4.htm | 23277 | 2019-02-21 16:03:02 |
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| exhibit3222018q4.htm | 10410 | 2019-02-21 16:03:02 |
| FilingSummary.xml | 39737 | 2019-02-21 16:03:02 |
| Financial_Report.xlsx | 83829 | 2019-02-21 16:03:02 |
| htld-20181231.htm | 1959734 | 2019-02-21 16:03:02 |
| htld-20181231.xsd | 50341 | 2019-02-21 16:03:02 |
| htld-20181231_cal.xml | 96605 | 2019-02-21 16:03:02 |
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| htld-20181231_lab.xml | 619692 | 2019-02-21 16:03:02 |
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| report.css | 2767 | 2019-02-21 16:03:02 |
| Show.js | 1085 | 2019-02-21 16:03:02 |