LONG-TERM DEBT AND FINANCING ARRANGEMENTS - Assets Securing Notes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Financing Arrangements
Total assets securing notes payable	$ 339,060	$ 336,222
Less accumulated depreciation	135,305	119,244
Net assets securing notes payable	$ 203,755	216,978
Weighted-average interest rate (as a percent)	3.30%
Interest paid, net of capitalized interest	$ 8,700	7,100	$ 8,700
Capitalized interest	300	300	$ 500
Revenue Equipment
Financing Arrangements
Total assets securing notes payable	300,922	294,700
Service, office, and other equipment
Financing Arrangements
Total assets securing notes payable	$ 38,138	$ 41,522