XML 41 R30.htm IDEA: XBRL DOCUMENT
v3.20.2

Stock-Based Compensation (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2019
Stock-Based Compensation [Abstract] |
Disclosure of Share-based Compensation Arrangements by Share-based Payment Award [Table Text Block] | The following table summarizes our restricted stock award activity for the years ended December 31, 2019, 2018 and 2017. The vesting dates for the awards vested in 2019 occurred relatively evenly throughout the year ended December 31, 2019. The fair value of awards vested during 2019, 2018 and 2017 was $1.8 million, $0.8 million and $0.6 million, respectively.
| 2019 |  |
| Number of Restricted Stock Awards ( in thousands) |  | Weighted Average Grant Date Fair Value
Unvested at January 1 | 26.5 |  |  | $ | 21.31 |
Granted | 114.0 |  |  | 19.88 |
Vested | (87.9) |  |  | 19.93 |
Forfeited | (0.5) |  |  | 17.11 |
Outstanding (unvested) at end of year | 52.1 |  |  | $ | 20.55 |
| 2018 |  |
| Number of Restricted Stock Awards ( in thousands) |  | Weighted Average Grant Date Fair Value
Unvested at January 1 | 53.7 |  |  | $ | 21.82 |
Granted | 10.0 |  |  | 18.58 |
Vested | (35.7) |  |  | 21.48 |
Forfeited | (1.5) |  |  | 17.11 |
Outstanding (unvested) at end of year | 26.5 |  |  | $ | 21.31 |
| 2017 |  |
| Number of Restricted Stock Awards (in thousands) |  | Weighted Average Grant Date Fair Value
Unvested at beginning of year | 53.0 |  |  | $ | 21.53 |
Granted | 27.0 |  |  | 22.98 |
Vested | (25.3) |  |  | 22.07 |
Forfeited | (1.0) |  |  | 17.11 |
Outstanding (unvested) at end of year | 53.7 |  |  | $ | 21.82 |

X
- Definition Stock-Based Compensation [Abstract] + References No definition available. + Details
Name: | htld_StockBasedCompensationAbstract
Namespace Prefix: | htld_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of share-based payment arrangement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5047-113901 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
Name: | us-gaap_DisclosureOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration