Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Revenue:
Total revenue	$ 173,566	$ 158,744
Operating expenses:
Salaries, wages, and related expenses	60,619	59,324
Fuel expense	27,181	25,402
Operations and maintenance	11,730	12,413
Revenue equipment rentals and purchased transportation	30,691	25,372
Operating taxes and licenses	2,660	2,735
Insurance and claims	8,685	8,718
Communications and utilities	1,741	1,628
General supplies and expenses	4,139	3,727
Depreciation and amortization, including gains and losses on disposition of property and equipment	19,695	19,116
Total operating expenses	167,141	158,435
Operating income	6,425	309
Interest expense, net	1,960	2,081
Income from equity method investment	(1,490)	(1,025)
Income (loss) before income taxes	5,955	(747)
Income tax expense (benefit)	1,538	(708)
Net income (loss)	$ 4,417	$ (39)
Income (loss) per share:
Basic and diluted net income (loss) per share (in dollars per share)	$ 0.24	$ 0
Basic weighted average shares outstanding (in shares)	18,331	18,256
Diluted weighted average shares outstanding (in shares)	18,406	18,256
Cargo and Freight [Member]
Revenue:
Total revenue	$ 150,463	$ 140,126
Fuel Surcharge [Member]
Revenue:
Total revenue	$ 23,103	$ 18,618