GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2022 USD ($)
Goodwill by reportable operating segment
Balance at the beginning of the period	$ 300,337
Purchase accounting adjustment	(1,262)
Balance at the end of the period	299,075
ArcBest
Goodwill by reportable operating segment
Balance at the beginning of the period	299,707
Purchase accounting adjustment	(1,262)
Balance at the end of the period	298,445
FleetNet
Goodwill by reportable operating segment
Balance at the beginning of the period	630
Balance at the end of the period	$ 630