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
Revenues
Freight revenue	$ 578,569us-gaap_CargoAndFreightRevenue	$ 538,933us-gaap_CargoAndFreightRevenue	$ 527,435us-gaap_CargoAndFreightRevenue
Fuel surcharge revenue	140,411us-gaap_ReimbursementRevenue	145,616us-gaap_ReimbursementRevenue	146,819us-gaap_ReimbursementRevenue
Total revenue	718,980us-gaap_Revenues	684,549us-gaap_Revenues	674,254us-gaap_Revenues
Operating expenses:
Salaries, wages, and related expenses	231,761us-gaap_LaborAndRelatedExpense	218,946us-gaap_LaborAndRelatedExpense	217,080us-gaap_LaborAndRelatedExpense
Fuel expense	168,856us-gaap_FuelCosts	186,002us-gaap_FuelCosts	194,841us-gaap_FuelCosts
Operations and maintenance	47,251us-gaap_MaintenanceCosts	50,043us-gaap_MaintenanceCosts	45,839us-gaap_MaintenanceCosts
Revenue equipment rentals and purchased transportation	111,772	102,954	85,010
Operating taxes and licenses	10,960	10,969	11,043
Insurance and claims	39,594	30,305	33,133
Communications and utilities	5,806	5,240	4,809
General supplies and expenses	16,950us-gaap_OtherCostAndExpenseOperating	16,002us-gaap_OtherCostAndExpenseOperating	16,068us-gaap_OtherCostAndExpenseOperating
Depreciation and amortization, including gains and losses on disposition of equipment	46,384	43,694	43,222
Total operating expenses	679,334us-gaap_OperatingExpenses	664,155us-gaap_OperatingExpenses	651,045us-gaap_OperatingExpenses
Operating income	39,646us-gaap_OperatingIncomeLoss	20,394us-gaap_OperatingIncomeLoss	23,209us-gaap_OperatingIncomeLoss
Other expenses (income):
Interest expense	10,807us-gaap_InterestExpenseDebt	10,400us-gaap_InterestExpenseDebt	12,697us-gaap_InterestExpenseDebt
Other	(13)us-gaap_OtherNonoperatingIncomeExpense	(3)us-gaap_OtherNonoperatingIncomeExpense	(13)us-gaap_OtherNonoperatingIncomeExpense
Other expenses, net	10,794us-gaap_NonoperatingIncomeExpense	10,397us-gaap_NonoperatingIncomeExpense	12,684us-gaap_NonoperatingIncomeExpense
Equity in income of affiliate	3,730	2,750	1,875
Income before income taxes	32,582	12,747	12,400
Income tax expense	14,774us-gaap_IncomeTaxExpenseBenefit	7,503us-gaap_IncomeTaxExpenseBenefit	6,335us-gaap_IncomeTaxExpenseBenefit
Net income	$ 17,808us-gaap_NetIncomeLoss	$ 5,244us-gaap_NetIncomeLoss	$ 6,065us-gaap_NetIncomeLoss
Basic income per share: (in Dollars per share)	$ 1.17us-gaap_EarningsPerShareBasic	$ 0.35us-gaap_EarningsPerShareBasic	$ 0.41us-gaap_EarningsPerShareBasic
Diluted income per share: (in Dollars per share)	$ 1.15us-gaap_EarningsPerShareDiluted	$ 0.35us-gaap_EarningsPerShareDiluted	$ 0.41us-gaap_EarningsPerShareDiluted
Basic weighted average shares outstanding (in Shares)	15,250	14,837	14,742
Diluted weighted average shares outstanding (in Shares)	15,517	15,039	14,808

The current period expense charged against earnings on long-lived, physical assets not used in production, and which are not intended for resale, to allocate or recognize the cost of such assets over their useful lives; or to record the reduction in book value of an intangible asset over the benefit period of such asset; or to reflect consumption during the period of an asset that is not used in production. Additionally, included are gains and losses on the sale of assets held for sale and property and equipment.

No definition available.