Note 15 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Assets Measured on Recurring Basis (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Available-for-sale securities	$ 152,236,508	$ 118,245,314
US Government Agencies Debt Securities [Member]
Available-for-sale securities	7,301,524	2,487,793
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	56,212,799	36,174,727
Corporate Debt Securities [Member]
Available-for-sale securities	27,638,726	15,535,187
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	13,331,303	13,811,371
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	47,752,156	50,236,236
Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	0
Fair Value, Recurring [Member]
Available-for-sale securities	152,237,000	118,245,000
Interest rate swaps	5,346,000	1,628,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	7,302,000	2,488,000
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	56,213,000	36,175,000
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	27,639,000	15,535,000
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	13,331,000	13,811,000
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	47,752,000	50,236,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities	0	0
Interest rate swaps	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	152,237,000	118,245,000
Interest rate swaps	5,346,000	1,628,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	7,302,000	2,488,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	56,213,000	36,175,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	27,639,000	15,535,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	13,331,000	13,811,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	47,752,000	50,236,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	0	0
Interest rate swaps	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	$ 0	$ 0