OPERATING SEGMENT DATA - (Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
OPERATING EXPENSES
Salaries, wages, and benefits	$ 350,187	$ 336,670	$ 685,016	$ 667,807
Rents, purchased transportation, and other costs of services	216,237	200,948	416,108	385,647
Fuel, supplies, and expenses	68,451	69,361	141,113	132,496
Depreciation and amortization	25,209	25,748	50,603	50,899
Other	35,187	27,246	64,141	53,844
Restructuring costs	363		1,994
Total consolidated operating expenses	$ 695,634	$ 659,973	$ 1,358,975	$ 1,290,693