OPERATING SEGMENT DATA - (Concentrations) (Details)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Revenues \| Customer concentration risk \| FleetNet \| Asset-Based and ArcBest segments
Concentrations
Concentration Risk, Percentage	14.00%	4.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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-Name Accounting Standards Codification
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-SubTopic 10
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-Section 50
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