Amortization Period of Tires

No definition available.

Name:	htld_AmortizationPeriodOfTires
Namespace Prefix:	htld_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

+ Details

Name:	us-gaap_Depreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The estimated or actual value of the asset at the end of its useful life or when it is no longer serviceable (cannot be used for its original purpose).

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentSalvageValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Useful life of long lived, physical assets used in the normal conduct of business and not intended for resale, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Examples include, but not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	htld_FinancialStatementLocationAxis=htld_CommunicationsAndUtilitiesExpenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=htld_TractorsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=htld_TrailersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=htld_LandImprovementsAndBuildingsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_LeaseholdImprovementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_FurnitureAndFixturesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=htld_ShopAndServiceEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=htld_RevenueequipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Significant Accounting Policies Property, Equipment and Depreciation (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment
Amortization Period of Tires	two years
Communications and Utilities Expense [Member]
Property, Plant and Equipment
Depreciation	$ 400,000	$ 700,000
Tractors [Member]
Property, Plant and Equipment
Property, Plant, and Equipment, Salvage Value	15,000
Trailers [Member]
Property, Plant and Equipment
Property, Plant, and Equipment, Salvage Value	$ 4,000
Minimum [Member] \| Land Improvements and Buildings [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	5 years
Minimum [Member] \| Leasehold Improvements [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	5 years
Minimum [Member] \| Furniture and Fixtures [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	3 years
Minimum [Member] \| Shop and Service Equipment [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	3 years
Minimum [Member] \| Revenue Equipment [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	5 years
Maximum [Member] \| Land Improvements and Buildings [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	30 years
Maximum [Member] \| Leasehold Improvements [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	25 years
Maximum [Member] \| Furniture and Fixtures [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	5 years
Maximum [Member] \| Shop and Service Equipment [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	10 years
Maximum [Member] \| Revenue Equipment [Member]
Property, Plant and Equipment
Property, Plant and Equipment, Useful Life	7 years