LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Assets securing notes (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Financing Arrangements
Total assets securing notes payable or held under finance leases	$ 288,662	$ 271,665
Less accumulated depreciation and amortization	105,185	88,696
Net assets securing notes payable or held under finance leases	183,477	182,969
Revenue equipment
Financing Arrangements
Total assets securing notes payable or held under finance leases	255,050	241,892
Service, office, and other equipment
Financing Arrangements
Total assets securing notes payable or held under finance leases	$ 33,612	$ 29,773