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Note 2 - Revenues (Details Textual)
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Number of Operating Segments 1  
Number of Major Customers 3 3
Customer Concentration Risk [Member] | Revenue Benchmark [Member]    
Number of Major Customers 4 4
Aquaplex [Member] | Customer Concentration Risk [Member] | Revenue Benchmark [Member]    
Number of Major Customers 1 1