GOODWILL AND INTANGIBLE ASSETS - Intangible (Details) - USD ($) $ in Thousands		12 Months Ended
	Oct. 01, 2020	Dec. 31, 2020	Dec. 31, 2019
Finite-lived intangible assets
Weighted Average Amortization Period		14 years
Cost		$ 53,701	$ 54,015
Accumulated Amortization		31,020	27,483
Net Value		22,681	26,532
Total intangible assets
Cost		86,001	86,315
Net Value		54,981	58,832
Impairment Assessment of Intangible Assets
Long-lived assets impairment			6,500
Impairment of indefinite-lived intangible assets	$ 0
ArcBest
Impairment Assessment of Intangible Assets
Long-lived assets impairment			6,500
Trade name
Indefinite-lived intangible assets
Net Value		$ 32,300	32,300
Customer relationships
Finite-lived intangible assets
Weighted Average Amortization Period		14 years
Cost		$ 52,721	52,721
Accumulated Amortization		30,477	26,667
Net Value		$ 22,244	26,054
Customer relationships | ArcBest
Impairment Assessment of Intangible Assets
Impairment of finite-lived intangible assets			6,000
Other intangible assets
Finite-lived intangible assets
Weighted Average Amortization Period		13 years
Cost		$ 980	1,294
Accumulated Amortization		543	816
Net Value		$ 437	478
Revenue Equipment | ArcBest
Impairment Assessment of Intangible Assets
Impairment of revenue equipment			$ 500