OPERATING SEGMENT DATA - Operating expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
OPERATING EXPENSES
Salaries, wages, and benefits	$ 1,550,859	$ 1,368,588	$ 1,408,409
Fuel, supplies, and expenses	324,380	250,221	316,047
Depreciation and amortization	124,221	118,391	112,466
Gain on sale of subsidiaries	(6,923)
Gain on sale of property and equipment	(8,520)	(2,376)	(5,247)
Other	129,571	129,850	126,146
Asset impairment			26,514
Total consolidated operating expenses	3,699,081	2,841,885	2,924,540
Operating Segments | Asset Based
OPERATING EXPENSES
Salaries, wages, and benefits	1,198,253	1,095,694	1,148,761
Fuel, supplies, and expenses	266,139	209,095	257,133
Operating taxes and licenses	49,461	49,300	50,209
Insurance	37,800	33,568	32,516
Communications and utilities	18,773	17,916	18,614
Depreciation and amortization	93,799	94,326	89,798
Rents and purchased transportation	364,345	250,159	221,479
Shared services	263,532	217,258	212,773
Gain on sale of property and equipment	(8,676)	(3,309)	(5,892)
Innovative technology costs	27,631	22,458	13,739
Other	2,009	6,701	3,488
Total consolidated operating expenses	2,313,066	1,993,166	2,042,618
Operating Segments | Asset Based | Land and structures
OPERATING EXPENSES
Gain on sale of property and equipment	(8,600)
Operating Segments | ArcBest
OPERATING EXPENSES
Purchased transportation	1,097,332	649,933	606,113
Supplies and expenses	10,531	9,627	10,789
Depreciation and amortization	11,387	9,714	11,344
Shared services	132,137	90,983	93,961
Gain on sale of subsidiaries	(6,923)
Other	9,765	9,203	9,860
Asset impairment			26,514
Total consolidated operating expenses	1,254,229	769,460	758,581
Operating Segments | ArcBest | Land and structures
OPERATING EXPENSES
Gain on sale of subsidiaries	(6,900)
Operating Segments | FleetNet
OPERATING EXPENSES
Depreciation and amortization	1,661	1,622	1,341
Total consolidated operating expenses	249,543	201,682	206,932
Other and eliminations
OPERATING EXPENSES
Depreciation and amortization	17,374	12,729	9,983
Total consolidated operating expenses	$ (117,757)	$ (122,423)	$ (83,591)