Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating revenue	$ 672,929us-gaap_Revenues	$ 659,214us-gaap_Revenues	$ 638,456us-gaap_Revenues
Operating expenses (income):
Salaries, wages and benefits	183,464us-gaap_LaborAndRelatedExpense	171,314us-gaap_LaborAndRelatedExpense	163,242us-gaap_LaborAndRelatedExpense
Purchased transportation	123,017mrtn_PurchasedTransportation	123,436mrtn_PurchasedTransportation	124,269mrtn_PurchasedTransportation
Fuel and fuel taxes	153,931us-gaap_FuelCosts	163,270us-gaap_FuelCosts	163,596us-gaap_FuelCosts
Supplies and maintenance	41,490us-gaap_MaintenanceCosts	40,582us-gaap_MaintenanceCosts	39,919us-gaap_MaintenanceCosts
Depreciation	68,243us-gaap_Depreciation	64,476us-gaap_Depreciation	60,904us-gaap_Depreciation
Operating taxes and licenses	7,140	7,110	6,741
Insurance and claims	27,240	23,681	20,718
Communications and utilities	5,798	5,212	4,939
Gain on disposition of revenue equipment	(4,387)us-gaap_GainLossOnDispositionOfAssets	(5,972)us-gaap_GainLossOnDispositionOfAssets	(5,302)us-gaap_GainLossOnDispositionOfAssets
Other	15,987us-gaap_OtherCostAndExpenseOperating	14,110us-gaap_OtherCostAndExpenseOperating	13,577us-gaap_OtherCostAndExpenseOperating
	621,923us-gaap_OperatingExpenses	607,219us-gaap_OperatingExpenses	592,603us-gaap_OperatingExpenses
Operating income	51,006us-gaap_OperatingIncomeLoss	51,995us-gaap_OperatingIncomeLoss	45,853us-gaap_OperatingIncomeLoss
Other	(667)us-gaap_NonoperatingIncomeExpense	(392)us-gaap_NonoperatingIncomeExpense	(48)us-gaap_NonoperatingIncomeExpense
Income before income taxes	51,673	52,387	45,901
Less: Income before income taxes attributable to noncontrolling interest		84	497
Income before income taxes attributable to Marten Transport, Ltd.	51,673	52,303	45,404
Provision for income taxes	21,839us-gaap_IncomeTaxExpenseBenefit	22,156us-gaap_IncomeTaxExpenseBenefit	18,137us-gaap_IncomeTaxExpenseBenefit
Net income	$ 29,834us-gaap_NetIncomeLoss	$ 30,147us-gaap_NetIncomeLoss	$ 27,267us-gaap_NetIncomeLoss
Basic earnings per common share (in Dollars per share)	$ 0.89us-gaap_EarningsPerShareBasic	$ 0.91us-gaap_EarningsPerShareBasic	$ 0.82us-gaap_EarningsPerShareBasic
Diluted earnings per common share (in Dollars per share)	$ 0.89us-gaap_EarningsPerShareDiluted	$ 0.90us-gaap_EarningsPerShareDiluted	$ 0.82us-gaap_EarningsPerShareDiluted
Dividends declared per common share (in Dollars per share)	$ 0.10	$ 0.083	$ 0.563

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