Consolidated Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Operating revenue	$ 223,046	$ 218,646
Operating expenses (income):
Salaries, wages and benefits	72,998	72,761
Purchased transportation	40,765	40,445
Fuel and fuel taxes	28,937	28,297
Supplies and maintenance	11,015	12,228
Depreciation	25,687	25,427
Operating taxes and licenses	2,712	2,639
Insurance and claims	11,446	12,284
Communications and utilities	2,083	1,985
Other	5,389	6,103
Total operating expenses	199,048	200,614
Operating income	23,998	18,032
Other	(10)	(97)
Income before income taxes	24,008	18,129
Income taxes expense	6,002	4,411
Net income	$ 18,006	$ 13,718
Basic earnings per common share (in dollars per share)	$ 0.22	$ 0.17
Diluted earnings per common share (in dollars per share)	0.22	0.17
Dividends declared per common share (in dollars per share)	$ 0.04	$ 0.027
Revenue Equipment [Member]
Operating expenses (income):
Gain on disposition of property, plant and equipment	$ (1,984)	$ (1,555)