Note 1 - Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Number of Operating Segments	5
Loss on Deposits Above FDIC Amount	$ 0
Accounts Receivable, Allowance for Credit Loss, Current	500,000	$ 348,000
Letters of Credit Outstanding, Amount	$ 16,100,000	$ 18,500,000
Revenue Benchmark [Member] \| Customer Concentration Risk [Member] \| Walmart [Member]
Concentration Risk, Percentage	21.00%	23.00%	24.00%
Revenue Benchmark [Member] \| Customer Concentration Risk [Member] \| The Coca-Cola Company [Member]
Concentration Risk, Percentage	7.00%	9.00%	12.00%
Revenue Benchmark [Member] \| Geographic Concentration Risk [Member] \| UNITED STATES
Concentration Risk, Percentage	99.00%	99.00%	99.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| Walmart [Member]
Concentration Risk, Percentage	22.00%	22.00%
Uninsured Risk [Member] \| Auto Liability Claim [Member]
Loss Contingency Range Possible Loss Per Claim	$ 1,000,000.0
Uninsured Risk [Member] \| Workers Compensation Liability Claim [Member]
Loss Contingency Range Possible Loss Per Claim	750,000
Insurance Claims [Member]
Letters of Credit Outstanding, Amount	16,100,000
Supplies and Maintenance Costs [Member]
Amortization, Total	$ 6,600,000	$ 6,400,000	$ 6,600,000
Tractor [Member]
Replacement Of Equipment Period After Purchase (Year)	3 years 10 months 24 days
Useful life (Year)	5 years
Property, Plant and Equipment, Salvage Value, Percentage	25.00%
Trailer [Member]
Replacement Of Equipment Period After Purchase (Year)	6 years 8 months 12 days
Useful life (Year)	7 years
Property, Plant and Equipment, Salvage Value, Percentage	35.00%
Refrigerated Containers [Member]
Useful life (Year)	12 years
Property, Plant and Equipment, Salvage Value, Percentage	0.00%
Tires In Service [Member]
Useful life (Year)	24 months

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Amount of allowance for credit loss on accounts receivable, classified as current.

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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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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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