Note 17 - Revenue and Business Segments (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Number of Operating Segments	5
Number of Reportable Segments	4
Customer Contract Term (Year)	1 year
Capitalized Contract Cost, Impairment Loss	$ 0	$ 0
Prepaid Expenses and Other Current Assets [Member]
Contract with Customer, Asset, after Allowance for Credit Loss, Total	1,500	1,700
Dedicated [Member]
Depreciation, Depletion and Amortization, Total	$ 41,400	34,600	$ 29,600
Dedicated [Member] \| Minimum [Member]
Customer Contract Term (Year)	3 years
Dedicated [Member] \| Maximum [Member]
Customer Contract Term (Year)	5 years
Truckload [Member]
Depreciation, Depletion and Amortization, Total	$ 54,700	54,000	52,200
Intermodal [Member]
Depreciation, Depletion and Amortization, Total	5,600	5,100	5,500
Brokerage [Member]
Depreciation, Depletion and Amortization, Total	$ 1,200	$ 1,500	$ 1,300

Duration of customer contracts.

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Amount of impairment loss for asset recognized from cost incurred to obtain or fulfill contract with customer.

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Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

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The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

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Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

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Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

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