Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Operating revenues	$ 534,644	$ 542,120	$ 1,030,298	$ 1,034,142
Operating expenses:
Salaries, wages and benefits	160,376	144,506	311,841	279,219
Fuel	57,381	92,131	110,141	183,206
Supplies and maintenance	46,388	45,887	94,045	91,741
Taxes and licenses	22,763	21,311	43,843	42,143
Insurance and claims	20,615	19,180	42,662	39,386
Depreciation	48,264	44,573	93,984	87,696
Rent and purchased transportation	124,952	128,239	238,700	239,885
Communications and utilities	3,837	3,409	7,515	6,908
Other	(2,142)	554	(2,828)	(1,813)
Total operating expenses	482,434	499,790	939,903	968,371
Operating income	52,210	42,330	90,395	65,771
Other expense (income):
Interest expense	583	136	1,058	230
Interest income	(697)	(660)	(1,328)	(1,315)
Other	135	(45)	225	(41)
Total other income	21	(569)	(45)	(1,126)
Income before income taxes	52,189	42,899	90,440	66,897
Income taxes	20,341	17,267	35,450	26,926
Net income	$ 31,848	$ 25,632	$ 54,990	$ 39,971
Earnings per share:
Basic	$ 0.44	$ 0.36	$ 0.76	$ 0.55
Diluted	0.44	0.35	0.76	0.55
Dividends declared per share	$ 0.050	$ 0.050	$ 0.100	$ 0.100
Weighted-average common shares outstanding:
Basic	71,945	72,091	72,005	72,382
Diluted	72,424	72,597	72,482	72,882