Consolidated Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating revenue	$ 186,960	$ 173,159
Operating expenses (income):
Salaries, wages and benefits	58,822	56,400
Purchased transportation	35,026	29,362
Fuel and fuel taxes	29,044	25,956
Supplies and maintenance	10,436	10,990
Depreciation	21,815	21,383
Operating taxes and licenses	2,287	2,247
Insurance and claims	10,290	8,914
Communications and utilities	1,683	1,581
Other	5,174	3,491
Total operating expenses	173,366	159,221
Operating income	13,594	13,938
Other	(189)	141
Income before income taxes	13,783	13,797
Income taxes expense	3,452	5,583
Net income	$ 10,331	$ 8,214
Basic earnings per common share (in dollars per share)	$ 0.19	$ 0.15
Diluted earnings per common share (in dollars per share)	0.19	0.15
Dividends declared per common share (in dollars per share)	$ 0.025	$ 0.015
Revenue Equipment [Member]
Operating expenses (income):
Gain on disposition of assets	$ (1,211)	$ (1,103)