OPERATING SEGMENT DATA - (Rev and Expenses) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
REVENUES
Revenues	$ 744,280	$ 713,923	$ 2,115,736	$ 2,012,005
OPERATING EXPENSES
Salaries, wages, and benefits	350,820	362,209	1,028,552	1,059,542
Fuel, supplies, and expenses	75,716	52,461	226,666	143,068
Depreciation and amortization	25,497	25,793	76,821	76,692
Gain on sale of property and equipment			(409)	(2,581)
Other	31,815	34,498	93,005	103,488
Restructuring costs	737		2,731
Total consolidated operating expenses	719,931	693,553	2,078,906	1,984,246
OPERATING INCOME
OPERATING INCOME	24,349	20,370	36,830	27,759
OTHER INCOME (COSTS)
Interest and dividend income	346	390	905	1,178
Interest and other related financing costs	(1,706)	(1,296)	(4,410)	(3,774)
Other, net	1,079	1,091	2,231	2,028
TOTAL OTHER INCOME (COSTS)	(281)	185	(1,274)	(568)
INCOME BEFORE INCOME TAXES	24,068	20,555	35,556	27,191
Operating Segments | Asset-Based
REVENUES
Revenues	517,417	509,001	1,496,310	1,434,315
OPERATING EXPENSES
Salaries, wages, and benefits	286,918	284,240	853,474	829,312
Fuel, supplies, and expenses	57,395	55,017	174,326	160,532
Operating taxes and licenses	11,712	12,237	35,726	36,239
Insurance	8,348	8,464	23,068	22,492
Communications and utilities	4,575	4,114	13,260	11,847
Depreciation and amortization	20,543	19,950	61,777	59,614
Rents and purchased transportation	55,381	58,221	154,995	145,439
Shared services	48,255	46,981	138,700	139,449
Gain on sale of property and equipment	(7)	(81)	(599)	(2,450)
Other	757	1,263	3,936	3,489
Restructuring costs	95		268
Total consolidated operating expenses	495,648	490,951	1,462,405	1,407,892
OPERATING INCOME
OPERATING INCOME	21,769	18,050	33,905	26,423
Operating Segments | ArcBest
REVENUES
Revenues	195,749	170,991	524,554	467,735
OPERATING EXPENSES
Purchased transportation	155,894	132,860	417,313	366,346
Supplies and expenses	3,853	3,263	11,265	9,282
Depreciation and amortization	3,015	3,684	9,511	10,497
Shared services	22,565	21,724	63,115	64,928
Other	2,817	3,191	8,155	8,232
Restructuring costs			875
Total consolidated operating expenses	188,144	164,722	510,234	459,285
OPERATING INCOME
OPERATING INCOME	7,605	6,269	14,320	8,450
Operating Segments | FleetNet
REVENUES
Revenues	39,568	39,073	116,307	124,417
OPERATING EXPENSES
Total consolidated operating expenses	38,695	38,952	113,730	122,716
OPERATING INCOME
OPERATING INCOME	873	121	2,577	1,701
Other and eliminations
REVENUES
Revenues	(8,454)	(5,142)	(21,435)	(14,462)
OPERATING EXPENSES
Restructuring costs	600		1,600
Total consolidated operating expenses	(2,556)	(1,072)	(7,463)	(5,647)
OPERATING INCOME
OPERATING INCOME	(5,898)	(4,070)	(13,972)	(8,815)
Nonunion Defined Benefit Pension Plan
OPERATING EXPENSES
Nonunion pension expense, including settlement	1,956	724	4,468	2,564
Nonunion Defined Benefit Pension Plan | Operating Segments | Asset-Based
OPERATING EXPENSES
Nonunion pension expense, including settlement	$ 1,676	$ 545	$ 3,474	$ 1,929