OPERATING SEGMENT DATA - (Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
OPERATING EXPENSES
Salaries, wages, and benefits	$ 305,220	$ 361,116	$ 650,166	$ 704,784
Rents, purchased transportation, and other costs of services	187,914	236,053	404,942	457,078
Fuel, supplies, and expenses	54,838	80,700	126,611	160,036
Depreciation and amortization	29,086	27,434	58,099	53,971
Other	29,887	30,987	60,707	63,669
Total consolidated operating expenses	$ 606,945	$ 736,290	$ 1,300,525	$ 1,439,538