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Note 1 - Summary of Significant Accounting Policies - Estimated Useful Lives (Details)	12 Months Ended
	Dec. 31, 2020
Tractor [Member]
Property, Plant and Equipment, Useful Life (Year)	5 years
Trailer [Member]
Property, Plant and Equipment, Useful Life (Year)	7 years
Refrigerated Containers [Member]
Property, Plant and Equipment, Useful Life (Year)	12 years
Service And Other Equipment [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)	3 years
Service And Other Equipment [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)	15 years
Building and Building Improvements [Member] | Minimum [Member]
Property, Plant and Equipment, Useful Life (Year)	20 years
Building and Building Improvements [Member] | Maximum [Member]
Property, Plant and Equipment, Useful Life (Year)	40 years

X

- 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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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

X

- Details

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