OPERATING SEGMENT DATA - Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
OPERATING INCOME
Operating income	$ 115,761	$ 87,561	$ 348,035	$ 194,051
OTHER INCOME (COSTS)
Interest and dividend income	1,147	323	1,614	1,037
Interest and other related financing costs	(1,749)	(2,072)	(5,551)	(6,774)
Other, net	(189)	338	(3,822)	2,641
TOTAL OTHER INCOME (COSTS)	(791)	(1,411)	(7,759)	(3,096)
INCOME BEFORE INCOME TAXES	114,970	86,150	340,276	190,955
Operating Segments | Asset Based
OPERATING INCOME
Operating income	109,312	83,618	306,002	177,584
Operating Segments | ArcBest
OPERATING INCOME
Operating income	15,384	10,182	63,979	33,574
Operating Segments | FleetNet
OPERATING INCOME
Operating income	881	1,269	4,190	3,430
Other and eliminations
OPERATING INCOME
Operating income	$ (9,816)	$ (7,508)	$ (26,136)	$ (20,537)