OPERATING SEGMENT DATA (Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	$ 149,951	$ 151,637	$ 159,017
DEPRECIATION AND AMORTIZATION EXPENSE	103,068	103,053	93,042
Amortization of intangibles	4,538	4,239	4,002
Operating Segments | Asset-Based
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	112,751	110,170	122,542
DEPRECIATION AND AMORTIZATION EXPENSE	82,507	80,331	71,320
Assets acquired through notes payable and capital leases	84,200	83,400	80,600
Operating Segments | ArcBest
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	9,823	6,154	24,219
DEPRECIATION AND AMORTIZATION EXPENSE	13,090	13,612	12,886
Amortization of intangibles	4,300	4,000	3,700
Operating Segments | FleetNet
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	1,089	403	1,007
DEPRECIATION AND AMORTIZATION EXPENSE	1,089	1,210	1,119
Amortization of intangibles	200	300	300
Other and eliminations
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	26,288	34,910	11,249
DEPRECIATION AND AMORTIZATION EXPENSE	$ 6,382	$ 7,900	$ 7,717