OPERATING SEGMENT DATA - (Operating Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
OPERATING EXPENSES
Salaries, wages, and benefits	$ 361,116	$ 355,913	$ 704,784	$ 684,670
Rents, purchased transportation, and other costs of services	236,053	253,540	457,078	477,296
Fuel, supplies, and expenses	80,700	84,884	160,036	163,530
Depreciation and amortization	27,434	27,187	53,971	53,673
Other	30,987	30,408	63,669	59,663
Multiemployer pension fund withdrawal liability charge		37,922		37,922
Restructuring costs		340		716
Total consolidated operating expenses	$ 736,290	$ 790,194	$ 1,439,538	$ 1,477,470