OPERATING SEGMENT DATA - (Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
OPERATING EXPENSES
Salaries, wages, and benefits	$ 343,668	$ 328,757
Rents, purchased transportation, and other costs of services	221,025	223,756
Fuel, supplies, and expenses	79,336	78,646
Depreciation and amortization	26,537	26,486
Other	32,682	29,255
Restructuring costs		376
Total consolidated operating expenses	$ 703,248	$ 687,276