OPERATING SEGMENT DATA - (Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
OPERATING EXPENSES
Salaries, wages, and benefits	$ 344,946	$ 343,668
Rents, purchased transportation, and other costs of services	217,028	221,025
Fuel, supplies, and expenses	71,773	79,336
Depreciation and amortization	29,013	26,537
Other	30,820	32,682
Total consolidated operating expenses	$ 693,580	$ 703,248