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Note 1 - Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Number of Operating Segments	5
Loss on Deposits Above FDIC Amount	$ 0
Accounts Receivable, Allowance for Credit Loss, Current	497,000	$ 500,000
Letters of Credit Outstanding, Amount	$ 20,700,000	$ 16,100,000
Revenue Benchmark [Member] \| Customer Concentration Risk [Member] \| Walmart [Member]
Concentration Risk, Percentage	19.00%	21.00%	23.00%
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	19.00%	22.00%
Uninsured Risk [Member] \| Auto Liability Claim [Member]
Loss Contingency Range Possible Loss Per Claim	$ 1,000,000
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	20,700,000
Supplies and Maintenance Costs [Member]
Amortization	$ 7,200,000	$ 6,600,000	$ 6,400,000
Tractor [Member]
Replacement Of Equipment Period After Purchase (Year)	4 years 1 month 6 days
Useful life (Year)	5 years
Property, Plant and Equipment, Salvage Value, Percentage	25.00%
Trailer [Member]
Replacement Of Equipment Period After Purchase (Year)	8 years
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