OPERATING SEGMENT DATA - Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
OPERATING INCOME
Operating income	$ 137,346	$ 74,299	$ 232,274	$ 106,490
OTHER INCOME (COSTS)
Interest and dividend income	361	322	467	714
Interest and other related financing costs	(1,863)	(2,274)	(3,802)	(4,702)
Other, net	(2,807)	1,111	(3,633)	2,303
Total other costs	(4,309)	(841)	(6,968)	(1,685)
INCOME BEFORE INCOME TAXES	133,037	73,458	225,306	104,805
Operating Segments | Asset Based
OPERATING INCOME
Operating income	116,656	63,911	196,690	93,966
Operating Segments | ArcBest
OPERATING INCOME
Operating income	27,479	15,127	48,595	23,392
Operating Segments | FleetNet
OPERATING INCOME
Operating income	1,592	1,138	3,309	2,161
Other and eliminations
OPERATING INCOME
Operating income	$ (8,381)	$ (5,877)	$ (16,320)	$ (13,029)