OPERATING SEGMENT DATA - (Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
OPERATING EXPENSES
Salaries, wages, and benefits									$ 1,345,672	$ 1,297,129	$ 1,231,130
Rents, purchased transportation, and other costs of services									823,683	790,612	754,495
Fuel, supplies, and expenses									270,138	292,039	353,489
Depreciation and amortization									103,053	93,042	86,222
Other									118,390	118,587	118,118
Restructuring costs	$ 10,300								10,313
Total consolidated operating expenses	$ 687,003	$ 693,553	$ 659,973	$ 630,720	$ 640,822	$ 675,942	$ 662,649	$ 611,996	$ 2,671,249	$ 2,591,409	$ 2,543,454