Document And Entity Information - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Feb. 29, 2016	Jun. 30, 2015
Entity Registrant Name	MARTEN TRANSPORT LTD
Entity Central Index Key	0000799167
Trading Symbol	mrtn
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Common Stock, Shares Outstanding (in shares)		32,390,025
Entity Public Float			$ 566,530
Document Type	10-K
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	FY
Amendment Flag	false