Note 9 - Amendment of Marten Transport, Ltd. 2015 Equity Incentive Plan (Details Textual) - 2015 Equity Incentive Plan [Member]	May 07, 2019 shares
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	1,300,000
Full Value Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	558,334

Number of additional shares authorized for issuance under share-based payment arrangement.

No definition available.

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration