Line of credit facility dividend restrictions percentage of net income limit.

No definition available.

Name:	mrtn_LineOfCreditFacilityDividendRestrictionsPercentageOfNetIncomeLimit
Namespace Prefix:	mrtn_
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Period Type:	instant

- Definition

The maximum amount for a waiver to pay for dividends as part of a line of credit facility.

+ References

No definition available.

+ Details

Name:	mrtn_LineOfCreditFacilityWaiverToPayDividendsMaximum
Namespace Prefix:	mrtn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187085-122770

+ Details

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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Namespace Prefix:
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Period Type:

- Details

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Namespace Prefix:
Data Type:	na
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Note 9 - Dividends (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended												12 Months Ended
	Dec. 31, 2020	Sep. 30, 2019	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2020	Aug. 31, 2019
Payments of Ordinary Dividends, Common Stock															$ 52,366	$ 42,089	$ 5,459
Line Of Credit Facility Dividend Restrictions Percentage Of Net Income Limit																		25.00%	25.00%
Line of Credit Facility, Waiver to Pay Dividends, Maximum																		$ 60,000	$ 65,000
Paid Quarterly [Member]
Payments of Ordinary Dividends, Common Stock															$ 52,400
Common Stock, Dividends, Per Share, Declared (in dollars per share)	$ 0.50		$ 0.04	$ 0.04	$ 0.027	$ 0.027	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.017	$ 0.017	$ 0.017	$ 0.017
Special Dividend [Member]
Common Stock, Dividends, Per Share, Declared (in dollars per share)		$ 0.433