Note 2 - Summary of Significant Accounting Policies (Details Textual) $ in Millions	12 Months Ended
Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Accounts Receivable, after Allowance for Credit Loss, Total	$ 21.9	$ 18.4	$ 12.0
Customer Concentration Risk [Member] \| Revenue Benchmark [Member] \| Commercial Air Handling [Member]
Number of Customers	9	9
Concentration Risk, Percentage	17.00%	14.00%
Customer Concentration Risk [Member] \| Revenue Benchmark [Member] \| Industrial and Transportation Products [Member]
Number of Customers	9	9
Concentration Risk, Percentage	23.00%	34.00%

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.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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