OPERATING SEGMENT DATA - (Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING EXPENSES
Salaries, wages, and benefits	$ 328,757	$ 332,590
Rents, purchased transportation, and other costs of services	223,756	199,871
Fuel, supplies, and expenses	78,646	72,662
Depreciation and amortization	26,486	25,394
Other	29,255	28,840
Restructuring costs	376	1,631
Total consolidated operating expenses	$ 687,276	$ 660,988