Unaudited Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating revenue
Revenue	$ 553,703	$ 475,021	$ 1,070,891	$ 925,781
Operating expenses
Salaries, wages, and benefits	181,418	144,500	350,446	286,503
Fuel and fuel taxes	89,253	43,783	154,296	84,187
Vehicle rents	24,336	21,547	48,630	43,010
Depreciation and amortization, net of (gain) loss on sale of property	14,929	23,205	33,646	45,587
Operating expenses and supplies	47,679	34,443	92,493	66,958
Insurance premiums and claims	23,401	18,933	43,540	40,710
Operating taxes and licenses	3,752	3,247	7,668	6,516
Communications and utilities	3,864	2,964	7,408	5,352
General and other operating expenses	18,418	16,004	35,737	30,904
Total operating expenses	547,235	466,115	1,064,633	908,877
Operating income	6,468	8,906	6,258	16,904
Other expense
Interest expense, net	4,586	3,557	8,393	7,244
Other expense	1,757	(20,191)	8,862	(20,191)
Nonoperating Income (Expense), Total	6,343	(16,634)	17,255	(12,947)
Income (loss) before income tax provision	125	25,540	(10,997)	29,851
Income tax provision (benefit)	79	6,443	(2,070)	8,093
Net total and comprehensive income (loss)	46	19,097	(8,927)	21,758
Net total and comprehensive income attributable to noncontrolling interest	600	1	529	124
Net total and comprehensive income (loss) attributable to controlling interest	$ (554)	$ 19,096	$ (9,456)	$ 21,634
Earnings (loss) per share
Basic earnings (loss) per share (in dollars per share)	$ (0.01)	$ 0.38	$ (0.19)	$ 0.43
Basic weighted average shares outstanding (in shares)	51,221	50,334	51,036	50,156
Diluted earnings (loss) per share (in dollars per share)	$ (0.01)	$ 0.37	$ (0.19)	$ 0.42
Diluted weighted average shares outstanding (in shares)	51,221	51,848	51,036	51,705
Cargo and Freight [Member]
Operating revenue
Revenue	$ 479,185	$ 437,533	$ 943,512	$ 855,174
Fuel Surcharge [Member]
Operating revenue
Revenue	74,518	37,488	127,379	70,607
Shipping and Handling [Member]
Operating expenses
Purchased transportation	$ 140,185	$ 157,489	$ 290,769	$ 299,150