OPERATING SEGMENT DATA - (Rev and Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
REVENUES
Revenues	$ 700,001	$ 651,088
OPERATING EXPENSES
Salaries, wages, and benefits	328,757	332,590
Fuel, supplies, and expenses	78,646	72,662
Depreciation and amortization	26,486	25,394
Gain on sale of property and equipment	(221)	(613)
Other	29,255	28,840
Restructuring costs	376	1,631
Total consolidated operating expenses	687,276	660,988
OPERATING INCOME
OPERATING INCOME (LOSS)	12,725	(9,900)
OTHER INCOME (COSTS)
Interest and dividend income	526	274
Interest and other related financing costs	(2,059)	(1,315)
Other, net	(2,201)	(1,706)
TOTAL OTHER INCOME (COSTS)	(3,734)	(2,747)
INCOME (LOSS) BEFORE INCOME TAXES	8,991	(12,647)
Calculated under Revenue Guidance in Effect before Topic 606
REVENUES
Revenues		651,088
Operating Segments | Asset-Based
REVENUES
Revenues	482,115
OPERATING EXPENSES
Salaries, wages, and benefits	269,779	279,380
Fuel, supplies, and expenses	62,193	58,390
Operating taxes and licenses	11,756	11,823
Insurance	6,628	7,118
Communications and utilities	4,521	4,517
Depreciation and amortization	20,930	20,519
Rents and purchased transportation	46,133	46,426
Shared services	45,607	43,503
Gain on sale of property and equipment	(133)	(617)
Other	1,299	1,505
Restructuring costs		140
Total consolidated operating expenses	468,713	472,704
OPERATING INCOME
OPERATING INCOME (LOSS)	13,402	(8,348)
Operating Segments | Asset-Based | Calculated under Revenue Guidance in Effect before Topic 606
REVENUES
Revenues		464,356
Operating Segments | ArcBest
REVENUES
Revenues	181,933
OPERATING EXPENSES
Purchased transportation	148,372	121,987
Supplies and expenses	3,230	3,670
Depreciation and amortization	3,408	3,266
Shared services	21,868	19,586
Other	1,881	2,464
Restructuring costs	9	810
Total consolidated operating expenses	178,768	151,783
OPERATING INCOME
OPERATING INCOME (LOSS)	3,165	1,093
Operating Segments | ArcBest | Calculated under Revenue Guidance in Effect before Topic 606
REVENUES
Revenues		152,876
Operating Segments | FleetNet
REVENUES
Revenues	47,759
OPERATING EXPENSES
Total consolidated operating expenses	46,238	39,217
OPERATING INCOME
OPERATING INCOME (LOSS)	1,521	1,021
Operating Segments | FleetNet | Calculated under Revenue Guidance in Effect before Topic 606
REVENUES
Revenues		40,238
Other and eliminations
REVENUES
Revenues	(11,806)
OPERATING EXPENSES
Total consolidated operating expenses	(6,443)	(2,716)
OPERATING INCOME
OPERATING INCOME (LOSS)	$ (5,363)	(3,666)
Other and eliminations | Calculated under Revenue Guidance in Effect before Topic 606
REVENUES
Revenues		$ (6,382)