OPERATING SEGMENT DATA - Operating Expenses by Category (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
OPERATING EXPENSES
Salaries, wages, and benefits	$ 453,283	$ 449,024	$ 892,806	$ 886,101
Rents, purchased transportation, and other costs of services	376,137	415,712	751,456	845,317
Fuel, supplies, and expenses	112,137	123,705	221,659	245,880
Depreciation and amortization	36,276	35,811	73,109	70,821
Contingent consideration	3,850	(10,000)	11,170	5,040
Other	47,303	47,096	92,770	93,124
Total consolidated operating expenses	$ 1,028,986	$ 1,061,348	$ 2,042,970	$ 2,146,283