Consolidated Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating revenue	$ 212,090	$ 197,024	$ 411,113	$ 383,984
Operating expenses (income):
Salaries, wages and benefits	68,613	63,250	132,137	122,072
Purchased transportation	38,668	35,048	76,917	70,074
Fuel and fuel taxes	30,952	31,742	58,629	60,786
Supplies and maintenance	11,502	10,251	22,623	20,687
Depreciation	23,462	22,193	46,005	44,008
Operating taxes and licenses	2,438	2,364	4,771	4,651
Insurance and claims	9,862	8,941	19,737	19,231
Communications and utilities	1,950	1,647	3,900	3,330
Gain on disposition of assets	(1,230)	(2,160)	(2,778)	(3,371)
Other	5,929	5,525	11,495	10,699
Total operating expenses	192,146	178,801	373,436	352,167
Operating income	19,944	18,223	37,677	31,817
Other	(395)	(138)	(673)	(327)
Income before income taxes	20,339	18,361	38,350	32,144
Income taxes expense	5,149	4,659	9,614	8,111
Net income	$ 15,190	$ 13,702	$ 28,736	$ 24,033
Basic earnings per common share (in dollars per share)	$ 0.28	$ 0.25	$ 0.53	$ 0.44
Diluted earnings per common share (in dollars per share)	0.28	0.25	0.52	0.44
Dividends declared per common share (in dollars per share)	$ 0.03	$ 0.025	$ 0.06	$ 0.05