OPERATING SEGMENT DATA - (Rev and Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
REVENUES
Revenues	$ 711,839	$ 700,001
OPERATING EXPENSES
Salaries, wages, and benefits	343,668	328,757
Fuel, supplies, and expenses	79,336	78,646
Depreciation and amortization	26,537	26,486
Gain on sale of property and equipment	(43)	(221)
Other	32,682	29,255
Restructuring costs		376
Total consolidated operating expenses	703,248	687,276
OPERATING INCOME
OPERATING INCOME	8,591	12,725
OTHER INCOME (COSTS)
Interest and dividend income	1,478	526
Interest and other related financing costs	(2,882)	(2,059)
Other, net	(591)	(2,201)
TOTAL OTHER INCOME (COSTS)	(1,995)	(3,734)
INCOME BEFORE INCOME TAXES	6,596	8,991
Operating Segments | Asset-Based
REVENUES
Revenues	506,079	482,115
OPERATING EXPENSES
Salaries, wages, and benefits	280,276	269,779
Fuel, supplies, and expenses	64,727	62,193
Operating taxes and licenses	12,398	11,756
Insurance	7,991	6,628
Communications and utilities	4,620	4,521
Depreciation and amortization	20,980	20,930
Rents and purchased transportation	49,912	46,133
Shared services	50,712	45,607
Gain on sale of property and equipment	(34)	(133)
Other	882	1,299
Total consolidated operating expenses	492,464	468,713
OPERATING INCOME
OPERATING INCOME	13,615	13,402
Operating Segments | ArcBest
REVENUES
Revenues	173,204	181,933
OPERATING EXPENSES
Purchased transportation	140,105	148,372
Supplies and expenses	2,774	3,230
Depreciation and amortization	3,151	3,408
Shared services	23,031	21,868
Other	2,413	1,881
Restructuring costs		9
Total consolidated operating expenses	171,474	178,768
OPERATING INCOME
OPERATING INCOME	1,730	3,165
Operating Segments | FleetNet
REVENUES
Revenues	53,259	47,759
OPERATING EXPENSES
Total consolidated operating expenses	51,771	46,238
OPERATING INCOME
OPERATING INCOME	1,488	1,521
Other and eliminations
REVENUES
Revenues	(20,703)	(11,806)
OPERATING EXPENSES
Total consolidated operating expenses	(12,461)	(6,443)
OPERATING INCOME
OPERATING INCOME	$ (8,242)	$ (5,363)