OPERATING SEGMENT DATA - Capital expenditures, depreciation and amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	$ 118,112	$ 105,051	$ 160,684
DEPRECIATION AND AMORTIZATION EXPENSE	124,221	118,391	112,466
Amortization of intangibles	5,357	4,012	4,367
Research and development costs	32,800	25,600
Operating Segments | Asset Based
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	96,180	85,135	122,437
DEPRECIATION AND AMORTIZATION EXPENSE	93,799	94,326	89,798
Assets acquired through notes payable	59,700	61,800	67,600
Operating Segments | ArcBest
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	9,565	1,258	3,909
DEPRECIATION AND AMORTIZATION EXPENSE	11,387	9,714	11,344
Amortization of intangibles	5,300	3,700	4,200
Operating Segments | FleetNet
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	1,174	675	590
DEPRECIATION AND AMORTIZATION EXPENSE	1,661	1,622	1,341
Amortization of intangibles		200	200
Operating Segments | Maximum | FleetNet
OPERATING SEGMENT DATA
Amortization of intangibles	100
Other and eliminations
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	11,193	17,983	33,748
DEPRECIATION AND AMORTIZATION EXPENSE	$ 17,374	$ 12,729	9,983
Assets acquired through notes payable			$ 23,200