Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Statement [Abstract]
Operating Revenue	$ 3,209,074	$ 2,881,433	$ 2,792,057
Operating Expenses:
Salaries, wages and employees’ benefits	1,487,847	1,301,280	1,169,539
Purchased transportation	237,306	238,688	315,896
Fuel, operating expenses and supplies	629,402	563,688	558,456
Operating taxes and licenses	80,128	69,542	63,824
Claims and insurance	77,649	67,984	56,601
Depreciation and amortization	210,105	178,845	157,203
Operating losses, net	4,477	910	50
Total operating expenses	2,726,914	2,420,937	2,321,569
Operating Income	482,160	460,496	470,488
Non-operating (Income) Expenses:
Interest expense	8,930	2,535	2,611
Interest income	(1,049)	(6,208)	(217)
Other, net	(1,729)	(2,058)	46
Non-operating (income) expenses, net	6,152	(5,731)	2,440
Income Before Income Taxes	476,008	466,227	468,048
Income Tax Expense	113,943	111,370	110,626
Net Income	$ 362,065	$ 354,857	$ 357,422
Weighted average common shares outstanding – basic	26,689	26,632	26,520
Weighted average common shares outstanding – diluted	26,802	26,763	26,674
Basic Earnings Per Share	$ 13.57	$ 13.32	$ 13.48
Diluted Earnings Per Share	$ 13.51	$ 13.26	$ 13.40