OPERATING SEGMENT DATA - Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
OPERATING EXPENSES
Salaries, wages, and benefits	$ 456,022	$ 444,164	$ 1,342,028	$ 1,301,944
Fuel, supplies, and expenses	122,700	125,349	369,466	365,213
Depreciation and amortization	37,141	34,229	107,962	103,509
Contingent consideration	(17,840)		(12,800)	810
Gain on sale of subsidiary				(402)
Lease impairment charges	30,162		30,162
Other	44,638	39,546	136,971	116,527
Total consolidated operating expenses	1,083,259	1,160,394	3,229,542	3,521,196
Operating right-of-use assets, Lease impairment charges	28,100		28,124
Operating Segments | Asset Based
OPERATING EXPENSES
Salaries, wages, and benefits	357,582	332,359	1,037,725	973,924
Fuel, supplies, and expenses	91,493	97,279	276,678	281,406
Operating taxes and licenses	13,865	13,089	41,938	38,405
Insurance	13,654	13,180	39,816	35,808
Communications and utilities	4,729	4,794	14,586	14,129
Depreciation and amortization	26,537	24,117	76,721	72,885
Rents and purchased transportation	79,233	123,714	271,899	348,249
Shared services	70,699	72,286	209,780	215,020
(Gain) loss on sale of property and equipment and lease impairment charges	540	(5,910)	905	(9,975)
Lease impairment charges	700		700
Innovative technology costs	7,300	6,068	21,711	20,982
Other	731	1,243	3,640	2,629
Total consolidated operating expenses	666,363	682,219	1,995,399	1,993,462
Noncash gain on a like-kind property exchange of a service center		(4,300)		(4,300)
Operating Segments | Asset-Light
OPERATING EXPENSES
Purchased transportation	365,217	425,567	1,078,482	1,382,107
Supplies and expenses	2,773	4,378	10,193	11,907
Depreciation and amortization	5,097	5,072	15,250	15,720
Shared services	47,411	56,371	147,825	164,554
Contingent consideration	(17,840)		(12,800)	810
Gain on sale of subsidiary				(402)
Lease impairment charges	14,407		14,407
Other	5,951	8,463	18,478	21,499
Total consolidated operating expenses	423,016	499,851	1,271,835	1,596,195
Other and eliminations
OPERATING EXPENSES
Lease impairment charges	15,100		15,100
Total consolidated operating expenses	$ (6,120)	$ (21,676)	$ (37,692)	$ (68,461)