CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Income Statement [Abstract]
Revenue	$ 5,340,490	$ 4,232,383	$ 3,495,644
Transportation costs	4,450,985	3,632,743	3,070,207
Gross margin	889,505	599,640	425,437
Costs and expenses:
Salaries and benefits	264,891	247,240	188,777
General and administrative	103,933	76,476	99,597
Depreciation and amortization	45,960	37,467	31,237
Total costs and expenses	414,784	361,183	319,611
Operating income	474,721	238,457	105,826
Other income (expense):
Interest expense, net	(6,632)	(7,302)	(9,343)
Other, net	(131)	(245)	(383)
Total other income (expense)	(6,763)	(7,547)	(9,726)
Income from continuing operations before income taxes	467,958	230,910	96,100
Income tax expense	111,010	59,436	22,541
Net income	356,948	171,474	73,559
Other comprehensive (loss) income:
Foreign currency translation adjustments	(7)	(16)	(5)
Total comprehensive income	$ 356,941	$ 171,458	$ 73,554
Earnings per share from continuing operations
Basic	$ 10.75	$ 5.13	$ 2.22
Diluted	10.64	5.06	2.19
Earnings per share net income
Earnings per share - basic	10.75	5.13	2.22
Earnings per share - diluted	$ 10.64	$ 5.06	$ 2.19
Basic weighted average number of shares outstanding	33,209	33,434	33,180
Diluted weighted average number of shares outstanding	33,559	33,892	33,543