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Note 5 - Debt (Details Textual) - USD ($)
Apr. 28, 2020
Mar. 25, 2019
Sep. 11, 2018
Mar. 31, 2020
Dec. 31, 2019
Jan. 31, 2019
Line of Credit, Current       $ 500,000 $ 500,000  
Revolving Credit Facility [Member]            
Line of Credit Facility, Maximum Borrowing Capacity   $ 750,000 $ 750,000      
Line of Credit, Current       $ 500,000   $ 500,000
Debt Instrument, Interest Rate, Stated Percentage       4.36%    
Revolving Credit Facility [Member] | Subsequent Event [Member]            
Debt Instrument, Term (Month) 180 days          
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]            
Debt Instrument, Basis Spread on Variable Rate   3.00% 2.25%