OPERATING SEGMENT DATA - Operating Expenses by Category (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
OPERATING EXPENSES
Salaries, wages, and benefits	$ 420,643	$ 359,395
Rents, purchased transportation, and other costs of services	646,879	309,338
Fuel, supplies, and expenses	99,547	73,149
Depreciation and amortization	34,823	30,354
Other	38,254	24,786
Total consolidated operating expenses	$ 1,240,146	$ 797,022