Consolidated Statements of Comprehensive Income - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Operating Revenue	$ 187,821	$ 154,128	$ 339,097	$ 306,530
Operating Expenses
Salaries, wages, and benefits	65,869	62,931	124,506	127,713
Rent and purchased transportation	3,127	1,009	3,874	1,973
Fuel	42,046	24,804	71,758	48,961
Operating Costs and Expenses	6,066	5,670	11,146	11,358
Cost, Direct Tax and License	3,352	3,413	6,562	7,034
Insurance and claims	6,339	4,678	11,905	10,117
Communications and utilities	1,126	967	2,204	2,193
Depreciation and amortization	24,309	25,956	47,620	52,882
Other operating expenses	12,244	5,204	18,042	10,756
Gain on disposal of property and equipment	(81,712)	(7,855)	(85,970)	(12,088)
Total operating expenses	82,766	126,777	211,647	260,899
Operating income	105,055	27,351	127,450	45,631
Interest income	260	175	406	312
Interest Expense	(174)	0	(174)	0
Income before income taxes	105,141	27,526	127,682	45,943
Federal and state income taxes	28,235	6,784	34,001	11,466
Net Income	76,906	20,742	93,681	34,477
Other comprehensive income, net of tax	0	0	0	0
Comprehensive income	$ 76,906	$ 20,742	$ 93,681	$ 34,477
Net income per share
Basic	$ 0.97	$ 0.26	$ 1.19	$ 0.43
Diluted	$ 0.97	$ 0.26	$ 1.19	$ 0.43
Weighted average shares outstanding
Basic	78,934	79,906	78,931	80,028
Diluted	78,959	79,957	78,956	80,081
Dividends declared per share	$ 0.02	$ 0.02	$ 0.04	$ 0.04