Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating revenues	$ 562,684	$ 501,221
Operating expenses:
Salaries, wages and benefits	182,794	160,839
Fuel	59,032	45,156
Supplies and maintenance	45,739	38,232
Taxes and licenses	22,493	20,786
Insurance and claims	21,158	19,840
Depreciation	55,506	55,336
Rent and purchased transportation	135,922	126,425
Communications and utilities	4,107	4,072
Other	818	4,563
Total operating expenses	527,569	475,249
Operating income	35,115	25,972
Other expense (income):
Interest expense	482	776
Interest income	(740)	(914)
Other	53	53
Total other income	(205)	(85)
Income before income taxes	35,320	26,057
Income taxes	7,513	10,038
Net income	$ 27,807	$ 16,019
Earnings per share:
Basic	$ 0.38	$ 0.22
Diluted	0.38	0.22
Dividends declared per share	$ 0.070	$ 0.060
Weighted-average common shares outstanding:
Basic	72,435	72,191
Diluted	72,671	72,447