OPERATING SEGMENT DATA - Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING INCOME
Operating income	$ 280,986	$ 98,278	$ 63,770
OTHER INCOME (COSTS)
Interest and dividend income	1,275	3,616	6,453
Interest and other related financing costs	(8,904)	(11,697)	(11,467)
Other, net	3,797	2,299	(7,285)
Total other costs	(3,832)	(5,782)	(12,299)
INCOME BEFORE INCOME TAXES	277,154	92,496	51,471
Operating Segments | Asset Based
OPERATING INCOME
Operating income	260,707	98,865	102,061
Operating Segments | ArcBest
OPERATING INCOME
Operating income	46,397	9,655	(20,189)
Operating Segments | FleetNet
OPERATING INCOME
Operating income	4,544	3,367	4,806
Other and eliminations
OPERATING INCOME
Operating income	$ (30,662)	$ (13,609)	$ (22,908)