Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING REVENUES:
Operating revenues		$ 810,807	$ 946,862	$ 707,120
OPERATING EXPENSES AND COSTS:
Salaries, wages and benefits		186,223	181,918	141,019
Operating supplies and expenses		160,527	166,005	102,228
Rents and purchased transportation		315,647	364,971	279,016
Depreciation		64,605	62,806	55,012
Insurance and claims		30,769	32,516	18,792
Other		23,769	18,128	12,294
Gain on disposition of equipment		(1,043)	(3,250)	(1,446)
Total operating expenses and costs		780,497	823,094	606,915
OPERATING INCOME		30,310	123,768	100,205
NON-OPERATING INCOME		7,446	3,168	10,339
INTEREST EXPENSE		(9,177)	(7,929)	(8,039)
INCOME BEFORE INCOME TAXES		28,579	119,007	102,505
FEDERAL & STATE INCOME TAX EXPENSE:
Current		7,277	13,794	8,157
Deferred		2,886	14,541	17,832
Total federal & state income tax expense		10,163	28,335	25,989
Net income		$ 18,416	$ 90,672	$ 76,516
EARNINGS PER COMMON SHARE:
Basic (in dollars per share)		$ 0.83	$ 4.08	$ 3.37
Diluted (in dollars per share)		$ 0.83	$ 4.04	$ 3.35
AVERAGE COMMON SHARES OUTSTANDING:
Basic (in shares)	[1]	22,056	22,246	22,715
Diluted (in shares)	[1]	22,197	22,436	22,864
Freight Transportation Service [Member]
OPERATING REVENUES:
Operating revenues		$ 706,114	$ 818,751	$ 641,253
Fuel Surcharge [Member]
OPERATING REVENUES:
Operating revenues		$ 104,693	$ 128,111	$ 65,867

[1] As adjusted for the Company’s 2-for-1 forward stock splits paid in August 2021 and March 2022, respectively.