OPERATING SEGMENT DATA (Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	$ 137,675	$ 149,951	$ 151,637
DEPRECIATION AND AMORTIZATION EXPENSE	108,635	103,068	103,053
Amortization of intangibles	4,521	4,538	4,239
Operating Segments | Asset-Based
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	116,505	112,751	110,170
DEPRECIATION AND AMORTIZATION EXPENSE	85,951	82,507	80,331
Assets acquired through notes payable and capital leases	86,800	84,200	83,400
Operating Segments | ArcBest
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	5,174	9,823	6,154
DEPRECIATION AND AMORTIZATION EXPENSE	13,750	13,090	13,612
Amortization of intangibles	4,300	4,300	4,000
Operating Segments | FleetNet
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	1,365	1,089	403
DEPRECIATION AND AMORTIZATION EXPENSE	1,140	1,089	1,210
Amortization of intangibles	200	200	200
Other and eliminations
OPERATING SEGMENT DATA
CAPITAL EXPENDITURES, GROSS	14,631	26,288	34,910
DEPRECIATION AND AMORTIZATION EXPENSE	7,794	$ 6,382	$ 7,900
Assets acquired through notes payable	$ 6,900