Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Revenue:
Freight revenue	$ 152,146	$ 137,588	$ 295,480	$ 263,833
Fuel surcharge revenue	23,305	35,066	47,186	70,778
Total revenue	175,451	173,654	342,666	334,611
Operating expenses:
Salaries, wages, and related expenses	59,131	56,141	117,384	109,015
Fuel expense	32,511	41,915	64,405	85,091
Operations and maintenance	12,140	11,533	22,937	23,564
Revenue equipment rentals and purchased transportation	25,957	27,612	49,166	52,946
Operating taxes and licenses	2,622	2,562	5,283	5,308
Insurance and claims	4,276	7,578	15,045	13,684
Communications and utilities	1,493	1,427	3,020	2,864
General supplies and expenses	4,252	4,529	7,933	8,338
Depreciation and amortization, including gains and losses on disposition of property and equipment	14,295	11,301	28,677	24,391
Total operating expenses	156,677	164,598	313,850	325,201
Operating income	18,774	9,056	28,816	9,410
Other (income) expenses:
Interest expense	$ 1,717	2,722	$ 3,920	5,473
Interest income		(4)		(8)
Other expenses, net	$ 1,717	2,718	$ 3,920	5,465
Equity in income of affiliate	1,335	850	2,720	1,650
Income before income taxes	18,392	7,188	27,616	5,595
Income tax expense	7,391	3,408	6,388	3,189
Net income	$ 11,001	$ 3,780	$ 21,228	$ 2,406
Income per share:
Basic net income per share (in dollars per share)	$ 0.60	$ 0.25	$ 1.17	$ 0.16
Diluted net income per share (in dollars per share)	$ 0.60	$ 0.25	$ 1.16	$ 0.16
Basic weighted average shares outstanding (in shares)	18,261	14,930	18,204	14,922
Diluted weighted average shares outstanding (in shares)	18,413	15,179	18,361	15,176