Note 4 - Securities - Available-for-sale Debt Securities (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Available-for-sale securities, amortized cost	$ 143,422,406	$ 117,152,760
Available-for-sale securities, gross unrealized gains	4,115,845	1,468,000
Available-for-sale securities, gross unrealized (losses)	(515,377)	(375,446)
Available-for-sale securities	147,022,874	118,245,314
US Government Agencies Debt Securities [Member]
Available-for-sale securities, amortized cost	8,532,000	2,499,755
Available-for-sale securities, gross unrealized gains	17,924	0
Available-for-sale securities, gross unrealized (losses)	(6,603)	(11,962)
Available-for-sale securities	8,543,321	2,487,793
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities, amortized cost	49,127,773	35,625,038
Available-for-sale securities, gross unrealized gains	2,241,588	675,382
Available-for-sale securities, gross unrealized (losses)	(90,355)	(125,693)
Available-for-sale securities	51,279,006	36,174,727
Corporate Debt Securities [Member]
Available-for-sale securities, amortized cost	27,055,325	15,395,190
Available-for-sale securities, gross unrealized gains	374,680	154,942
Available-for-sale securities, gross unrealized (losses)	(159,072)	(14,945)
Available-for-sale securities	27,270,933	15,535,187
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities, amortized cost	10,838,275	13,788,728
Available-for-sale securities, gross unrealized gains	123,752	52,035
Available-for-sale securities, gross unrealized (losses)	(165,184)	(29,392)
Available-for-sale securities	10,796,843	13,811,371
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities, amortized cost	47,869,033	49,844,049
Available-for-sale securities, gross unrealized gains	1,357,901	585,641
Available-for-sale securities, gross unrealized (losses)	(94,163)	(193,454)
Available-for-sale securities	$ 49,132,771	$ 50,236,236