Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Operating Revenue	$ 152,612	$ 162,282	$ 459,142	$ 489,473
Operating Expenses
Salaries, wages, and benefits	62,733	67,178	190,446	205,579
Rent and purchased transportation	950	999	2,922	3,635
Fuel	25,258	21,218	74,220	65,445
Operating Costs and Expenses	5,372	7,118	16,729	21,516
Cost, Direct Tax and License	3,311	3,664	10,345	11,229
Insurance and claims	5,053	4,827	15,171	16,034
Communications and utilities	1,218	1,398	3,412	4,091
Depreciation and amortization	25,280	27,625	78,162	81,427
Other operating expenses	5,418	6,637	16,173	19,602
Gain on disposal of property and equipment	(15,254)	(5,721)	(27,341)	(8,739)
Total operating expenses	119,339	134,943	380,239	419,819
Operating income	33,273	27,339	78,903	69,654
Interest income	181	171	493	704
Income before income taxes	33,454	27,510	79,396	70,358
Federal and state income taxes	8,988	6,796	20,454	17,224
Net Income	24,466	20,714	58,942	53,134
Other comprehensive income, net of tax	0	0	0	0
Comprehensive income	$ 24,466	$ 20,714	$ 58,942	$ 53,134
Net income per share
Basic	$ 0.31	$ 0.25	$ 0.74	$ 0.65
Diluted	$ 0.31	$ 0.25	$ 0.74	$ 0.65
Weighted average shares outstanding
Basic	79,336	81,370	79,795	81,530
Diluted	79,364	81,404	79,839	81,587
Dividends declared per share	$ 0.52	$ 0.02	$ 0.56	$ 0.06