LONG-TERM DEBT AND FINANCING ARRANGEMENTS (Assets Sec) (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Financing Arrangements
Total assets securing notes payable or held under capital leases	$ 251,433	$ 272,330
Less accumulated depreciation and amortization	84,766	87,691
Net assets securing notes payable or held under capital leases	166,667	184,639
Revenue equipment
Financing Arrangements
Total assets securing notes payable or held under capital leases	249,053	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	$ 100	$ 100