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Note 1 - Summary of Significant Accounting Policies (Details Textual)	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Number of Operating Segments	5
Loss on Deposits Above FDIC Amount	$ 0
Number of Reportable Segments	4
Revenue Benchmark [Member] \| Customer Concentration Risk [Member] \| Walmart [Member]
Concentration Risk, Percentage	24.00%	17.00%	15.00%
Revenue Benchmark [Member] \| Customer Concentration Risk [Member] \| The Coca-Cola Company [Member]
Concentration Risk, Percentage	12.00%	14.00%	13.00%
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	24.00%	21.00%
Accounts Receivable [Member] \| Customer Concentration Risk [Member] \| The Coca-Cola Company [Member]
Concentration Risk, Percentage	8.00%	9.00%
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	17,000,000.0	$ 15,700,000
Supplies and Maintenance Costs [Member]
Amortization, Total	$ 6,600,000	$ 6,900,000	$ 7,000,000.0
Tractor [Member]
Replacement Of Equipment Period After Purchase (Year)	4 years 1 month 6 days
Property, Plant and Equipment, 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 4 months 24 days
Property, Plant and Equipment, Useful Life (Year)	7 years
Property, Plant and Equipment, Salvage Value, Percentage	35.00%
Refrigerated Containers [Member]
Property, Plant and Equipment, Useful Life (Year)	12 years
Property, Plant and Equipment, Salvage Value, Percentage	0.00%
Tires In Service [Member]
Property, Plant and Equipment, Useful Life (Year)	24 months