LONG-TERM DEBT AND FINANCING ARRANGEMENTS (Assets Sec) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Financing Arrangements
Total assets securing notes payable or held under capital leases	$ 260,208	$ 272,330
Less accumulated depreciation and amortization	92,558	87,691
Net assets securing notes payable or held under capital leases	167,650	184,639
Revenue equipment
Financing Arrangements
Total assets securing notes payable or held under capital leases	257,827	269,950
Land and structures (service centers)
Financing Arrangements
Total assets securing notes payable or held under capital leases	1,794	1,794
Software
Financing Arrangements
Total assets securing notes payable or held under capital leases	486	486
Service, office, and other equipment
Financing Arrangements
Total assets securing notes payable or held under capital leases	$ 101	$ 100