Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING REVENUES:
Operating revenues	$ 707,120	$ 486,825	$ 514,177
OPERATING EXPENSES AND COSTS:
Salaries, wages and benefits	141,019	124,098	129,738
Operating supplies and expenses	102,228	84,275	98,420
Rents and purchased transportation	279,016	165,984	168,399
Depreciation	55,012	56,168	55,107
Insurance and claims	18,792	8,866	35,622
Other	12,294	13,138	13,761
(Gain) Loss on disposition of equipment	(1,446)	373	583
Total operating expenses and costs	606,915	452,902	501,630
OPERATING INCOME	100,205	33,923	12,547
NON-OPERATING INCOME (EXPENSE)	10,339	(1,699)	6,222
INTEREST EXPENSE	(8,039)	(8,815)	(8,654)
INCOME BEFORE INCOME TAXES	102,505	23,409	10,115
FEDERAL & STATE INCOME TAX EXPENSE:
Current	8,157	220	590
Deferred	17,832	5,362	1,625
Total federal & state income tax expense	25,989	5,582	2,215
Net income	$ 76,516	$ 17,827	$ 7,900
EARNINGS PER COMMON SHARE:
Basic (in dollars per share)	$ 6.74	$ 1.55	$ 0.68
Diluted (in dollars per share)	$ 6.69	$ 1.55	$ 0.67
AVERAGE COMMON SHARES OUTSTANDING:
Basic (in shares)	11,357	11,504	11,663
Diluted (in shares)	11,432	11,536	11,760
Freight Transportation Service [Member]
OPERATING REVENUES:
Operating revenues	$ 641,253	$ 438,987	$ 439,511
Fuel Surcharge [Member]
OPERATING REVENUES:
Operating revenues	$ 65,867	$ 47,838	$ 74,666