Note 6 - Accrued Interest Receivable - Summary of Accrued Interest Receivable (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Accrued interest receivable	$ 875,104	$ 824,542
US States and Political Subdivisions Debt Securities [Member]
Accrued interest receivable	111,607	114,424
Residential Mortgage Backed Securities [Member]
Accrued interest receivable	32,907	38,805
Loans Receivable [Member]
Accrued interest receivable	$ 730,590	$ 671,313