OPERATING SEGMENT DATA - Operating Expenses by Category (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
OPERATING EXPENSES
Salaries, wages, and benefits		$ 1,781,304	$ 1,728,653	$ 1,527,533
Rents, purchased transportation, and other costs of services		1,642,669	2,100,663	1,349,106
Fuel, supplies, and expenses		479,688	488,009	360,657
Depreciation and amortization		145,349	138,159	122,560
Contingent consideration		(19,100)	18,300
Lease impairment charges	$ 30,200	30,162
Other		194,752	160,698	129,351
Total consolidated operating expenses		4,254,824	4,634,482	3,489,207
Gain on sale of subsidiaries			402	6,923
Gain on sale of property and equipment		(4,797)	11,650	8,520
Innovative technology costs		52,400	40,800	32,800
Operating Segments | Asset Based
OPERATING EXPENSES
Salaries, wages, and benefits		1,379,756	1,293,487	1,198,253
Fuel, supplies, and expenses		361,355	378,558	266,139
Depreciation and amortization		104,165	97,322	93,799
Lease impairment charges		700
Other		4,829	4,175	2,009
Total consolidated operating expenses		2,617,852	2,629,767	2,313,066
Gain related to sale of property and equipment and sale of replaced equipment and like-kind exchange of service center property			12,500
Operating Segments | Asset Based | Land and structures
OPERATING EXPENSES
Gain on sale of property and equipment				8,600
Operating Segments | Asset-Light
OPERATING EXPENSES
Depreciation and amortization		20,370	20,730	11,387
Contingent consideration		(19,100)	18,300
Lease impairment charges		14,407
Other		25,745	31,163	11,635
Total consolidated operating expenses		1,692,916	2,086,547	1,254,229
Estimated settlement expense		9,500
Gain on sale of subsidiaries			402	6,923
Other and eliminations
OPERATING EXPENSES
Depreciation and amortization		20,814	20,107	17,374
Lease impairment charges		15,100
Total consolidated operating expenses		$ (55,944)	$ (81,832)	$ (78,088)