Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Income Statement [Abstract]
Operating Revenue	$ 147,908	$ 151,279	$ 429,589	$ 463,800
Operating Expenses
Salaries, wages, and benefits	60,909	55,126	168,137	174,694
Rent and purchased transportation	1,936	4,067	6,216	15,652
Fuel	25,211	27,460	71,730	85,340
Operating Costs and Expenses	6,260	6,469	17,730	20,970
Cost, Direct Tax and License	3,416	3,938	10,808	12,039
Insurance and claims	3,256	4,407	12,030	12,862
Communications and utilities	1,211	1,416	3,538	4,852
Depreciation and amortization	25,572	25,133	70,414	75,490
Other operating expenses	5,993	5,287	16,351	17,083
Gain on disposal of property and equipment	(12,595)	(7,156)	(23,978)	(15,410)
Total operating expenses	121,169	126,147	352,976	403,572
Operating income	26,739	25,132	76,613	60,228
Interest income	1,128	586	3,502	1,351
Interest Expense	(452)	0	(452)	0
Income before income taxes	27,415	25,718	79,663	61,579
Federal and state income taxes	6,914	6,662	19,483	11,342
Net income	20,501	19,056	60,180	50,237
Other comprehensive income, net of tax	0	0	0	0
Comprehensive income	$ 20,501	$ 19,056	$ 60,180	$ 50,237
Net income per share
Basic	$ 0.25	$ 0.23	$ 0.73	$ 0.61
Diluted	$ 0.25	$ 0.23	$ 0.73	$ 0.61
Weighted average shares outstanding
Basic	81,992	81,965	81,965	82,530
Diluted	82,040	81,992	82,008	82,564
Dividends declared per share	$ 0.02	$ 0.02	$ 0.06	$ 0.06