Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Operating revenues	$ 629,735	$ 528,643	$ 1,811,549	$ 1,549,372
Operating expenses:
Salaries, wages and benefits	201,606	170,238	580,515	500,620
Fuel	67,072	50,266	191,769	140,551
Supplies and maintenance	47,136	41,986	138,556	120,276
Taxes and licenses	18,463	21,671	63,607	64,095
Insurance and claims	22,011	20,669	73,858	60,336
Depreciation	58,382	53,578	170,439	162,619
Rent and purchased transportation	147,870	126,087	435,225	377,146
Communications and utilities	3,993	4,199	12,028	12,158
Other	(184)	4,075	(3,732)	12,812
Total operating expenses	566,349	492,769	1,662,265	1,450,613
Operating income	63,386	35,874	149,284	98,759
Other expense (income):
Interest expense	870	492	1,842	1,892
Interest income	(646)	(766)	(2,079)	(2,556)
Other	41	88	172	293
Total other expense (income)	265	(186)	(65)	(371)
Income before income taxes	63,121	36,060	149,349	99,130
Income taxes	15,607	13,543	35,764	37,375
Net income	$ 47,514	$ 22,517	$ 113,585	$ 61,755
Earnings per share:
Basic	$ 0.67	$ 0.31	$ 1.58	$ 0.85
Diluted	0.66	0.31	1.57	0.85
Dividends declared per share	$ 0.090	$ 0.070	$ 0.250	$ 0.200
Weighted-average common shares outstanding:
Basic	71,436	72,298	72,001	72,239
Diluted	71,752	72,601	72,300	72,517