Note 3 - Securities - Available-for-sale Securities by Maturity (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
1-5 years, amortized cost	$ 1,000,000
1-5 years, fair value	999,531
6-10 years, amortized cost	39,772,344
6-10 years, fair value	39,833,474
After 10 years, amortized cost	67,239,904
After 10 years, fair value	68,252,095
Not due on a single maturity date, amortized cost	177,601,112	$ 159,249,817
Available-for-sale securities	179,334,565	164,120,869
Commercial Mortgage Backed Securities [Member]
Not due on a single maturity date, amortized cost	6,406,588
Not due on a single maturity date, fair value	6,474,726
Not due on a single maturity date, amortized cost	6,406,588
Available-for-sale securities	6,474,726
Residential Mortgage Backed Securities [Member]
Not due on a single maturity date, amortized cost	9,418,436
Not due on a single maturity date, fair value	9,531,810
Not due on a single maturity date, amortized cost	9,418,436	9,249,375
Available-for-sale securities	9,531,810	9,452,097
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Not due on a single maturity date, amortized cost	53,763,840
Not due on a single maturity date, fair value	54,242,929
Not due on a single maturity date, amortized cost	53,763,840	49,053,252
Available-for-sale securities	$ 54,242,929	$ 50,370,815

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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