Note 4 - Securities - Available-for-sale Securities by Maturity (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
1-5 years, amortized cost	$ 150,000
1-5 years, fair value	150,324
5-10 years, amortized cost	36,006,625
5-10 years, fair value	36,533,558
After 10 years, amortized cost	48,558,473
After 10 years, fair value	50,409,378
Available-for-sale securities, amortized cost	143,422,406	$ 117,152,760
Available-for-sale securities	147,022,874	118,245,314
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Not due on a single maturity date, amortized cost	10,838,275
Not due on a single maturity date, fair value	10,796,843
Available-for-sale securities, amortized cost	10,838,275	13,788,728
Available-for-sale securities	10,796,843	13,811,371
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Not due on a single maturity date, amortized cost	47,869,033
Not due on a single maturity date, fair value	49,132,771
Available-for-sale securities, amortized cost	47,869,033	49,844,049
Available-for-sale securities	$ 49,132,771	$ 50,236,236

Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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