GOODWILL AND INTANGIBLE ASSETS - Goodwill (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 01, 2020	Dec. 31, 2021	Dec. 31, 2019
Goodwill by reportable operating segment
Balance at the beginning of the period		$ 88,320
Goodwill acquired		213,969
Goodwill divested		(1,952)
Balance at the end of the period		300,337
Accumulated impairment		(20,000)
Goodwill impairment	$ 0
ArcBest
Goodwill by reportable operating segment
Balance at the beginning of the period		87,690
Goodwill acquired		213,969
Goodwill divested		(1,952)
Balance at the end of the period		299,707
Accumulated impairment		(20,000)
Goodwill impairment			$ 20,000
FleetNet
Goodwill by reportable operating segment
Balance at the beginning of the period		630
Balance at the end of the period		$ 630