OPERATING SEGMENT DATA - (Rev and Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
REVENUES
Revenues	$ 701,399	$ 711,839
OPERATING EXPENSES
Salaries, wages, and benefits	344,946	343,668
Fuel, supplies, and expenses	71,773	79,336
Depreciation and amortization	29,013	26,537
Gain on sale of property and equipment	(2,130)	(43)
Other	30,820	32,682
Total consolidated operating expenses	693,580	703,248
OPERATING INCOME
Operating income	7,819	8,591
OTHER INCOME (COSTS)
Interest and dividend income	1,375	1,478
Interest and other related financing costs	(2,947)	(2,882)
Other, net	(3,862)	(591)
TOTAL OTHER INCOME (COSTS)	(5,434)	(1,995)
INCOME BEFORE INCOME TAXES	2,385	6,596
Operating Segments | Asset-Based
REVENUES
Revenues	515,713	506,079
OPERATING EXPENSES
Salaries, wages, and benefits	283,838	280,276
Fuel, supplies, and expenses	61,225	63,972
Operating taxes and licenses	12,794	12,398
Insurance	7,824	7,991
Communications and utilities	4,711	4,616
Depreciation and amortization	23,270	20,961
Rents and purchased transportation	55,770	49,306
Shared services	48,885	50,295
Gain on sale of property and equipment	(2,164)	(34)
Innovative technology costs	4,533	1,802
Other	1,787	881
Total consolidated operating expenses	502,473	492,464
OPERATING INCOME
Operating income	13,240	13,615
Operating Segments | ArcBest
REVENUES
Revenues	164,775	173,204
OPERATING EXPENSES
Purchased transportation	137,182	140,105
Supplies and expenses	2,280	2,774
Depreciation and amortization	2,470	3,151
Shared services	21,727	23,031
Other	2,525	2,413
Total consolidated operating expenses	166,184	171,474
OPERATING INCOME
Operating income	(1,409)	1,730
Operating Segments | FleetNet
REVENUES
Revenues	52,439	53,259
OPERATING EXPENSES
Total consolidated operating expenses	51,399	51,771
OPERATING INCOME
Operating income	1,040	1,488
Other and eliminations
REVENUES
Revenues	(31,528)	(20,703)
OPERATING EXPENSES
Total consolidated operating expenses	(26,476)	(12,461)
OPERATING INCOME
Operating income	$ (5,052)	$ (8,242)