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Note 2 - Certificates of Deposit (Details Textual) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Certificates Of Deposit Maximum Value Per Deposit $ 250,000  
Certificates of Deposit, at Carrying Value, Current and Noncurrent 0 $ 2,697,000
Payments to Acquire Investments, Total 3,960 255,578
Certificates of Deposit [Member]    
Payments to Acquire Investments, Total 1,985,920 2,456,000
Proceeds from Sale, Maturity and Collection of Investments, Total $ 4,682,920 $ 3,854,000