Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Operating revenues	$ 627,533	$ 619,130	$ 1,223,650	$ 1,181,814
Operating expenses:
Salaries, wages and benefits	206,001	196,115	408,800	378,909
Fuel	61,064	65,665	117,202	124,697
Supplies and maintenance	44,371	45,681	90,056	91,420
Taxes and licenses	23,643	22,651	46,544	45,144
Insurance and claims	20,992	30,689	43,701	51,847
Depreciation	61,437	56,551	122,196	112,057
Rent and purchased transportation	146,176	151,433	279,012	287,355
Communications and utilities	3,903	3,928	7,914	8,035
Other	1,504	(4,366)	1,764	(3,548)
Total operating expenses	569,091	568,347	1,117,189	1,095,916
Operating income	58,442	50,783	106,461	85,898
Other expense (income):
Interest expense	1,429	490	2,287	972
Interest income	(989)	(693)	(1,892)	(1,433)
Other	58	78	(58)	131
Total other expense (income)	498	(125)	337	(330)
Income before income taxes	57,944	50,908	106,124	86,228
Income taxes	14,626	12,644	26,720	20,157
Net income	$ 43,318	$ 38,264	$ 79,404	$ 66,071
Earnings per share:
Basic	$ 0.62	$ 0.53	$ 1.14	$ 0.91
Diluted	$ 0.62	$ 0.53	$ 1.13	$ 0.91
Weighted-average common shares outstanding:
Basic	69,593	72,144	69,932	72,289
Diluted	69,893	72,376	70,229	72,522