Document And Entity Information	6 Months Ended
	Jun. 30, 2012	Aug. 01, 2012
Document and Entity Information [Abstract]
Entity Registrant Name	MARTEN TRANSPORT LTD
Document Type	10-Q
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		22,071,249
Amendment Flag	false
Entity Central Index Key	0000799167
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Document Period End Date	Jun. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q2