Consolidated Statements Of Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Operating revenues	$ 498,681	$ 534,644	$ 981,483	$ 1,030,298
Operating expenses:
Salaries, wages and benefits	159,699	160,376	316,436	311,841
Fuel	39,336	57,381	71,396	110,141
Supplies and maintenance	42,417	46,388	89,532	94,045
Taxes and licenses	21,826	22,763	42,813	43,843
Insurance and claims	21,931	20,615	40,278	42,662
Depreciation	50,904	48,264	101,068	93,984
Rent and purchased transportation	127,303	124,952	245,279	238,700
Communications and utilities	3,995	3,837	7,904	7,515
Other	1,717	(2,142)	4,737	(2,828)
Total operating expenses	469,128	482,434	919,443	939,903
Operating income	29,553	52,210	62,040	90,395
Other expense (income):
Interest expense	596	583	1,090	1,058
Interest income	(1,109)	(697)	(2,099)	(1,328)
Other	57	135	102	225
Total other income	(456)	21	(907)	(45)
Income before income taxes	30,009	52,189	62,947	90,440
Income taxes	11,703	20,341	24,549	35,450
Net income	$ 18,306	$ 31,848	$ 38,398	$ 54,990
Earnings per share:
Basic	$ 0.25	$ 0.44	$ 0.53	$ 0.76
Diluted	0.25	0.44	0.53	0.76
Dividends declared per share	$ 0.060	$ 0.050	$ 0.120	$ 0.100
Weighted-average common shares outstanding:
Basic	72,048	71,945	72,036	72,005
Diluted	72,366	72,424	72,349	72,482