Note 4 - Securities - Available-for-sale Securities by Maturity (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
1-5 years, amortized cost	$ 386,057
1-5 years, fair value	391,105
5-10 years, amortized cost	15,321,979
5-10 years, fair value	15,495,164
After 10 years, amortized cost	29,452,145
After 10 years, fair value	30,198,857
Available-for-sale securities, amortized cost	104,828,360	$ 88,102,659
Available-for-sale securities	106,353,702	86,266,197
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Not due on a single maturity date, amortized cost	10,963,720
Not due on a single maturity date, fair value	10,972,903
Available-for-sale securities, amortized cost	10,963,720
Available-for-sale securities	10,972,903
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Not due on a single maturity date, amortized cost	48,704,459
Not due on a single maturity date, fair value	49,295,673
Available-for-sale securities, amortized cost	48,704,459	50,632,011
Available-for-sale securities	$ 49,295,672	$ 49,476,750

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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