Note 13 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Assets Measured on Recurring Basis (Details) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Available-for-sale securities	$ 179,334,565	$ 164,120,869
US Government Agencies Debt Securities [Member]
Available-for-sale securities	6,984,688	6,283,634
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	67,466,062	61,969,054
Corporate Debt Securities [Member]
Available-for-sale securities	34,634,350	30,600,822
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	54,242,929	50,370,815
Fair Value, Recurring [Member]
Available-for-sale securities	179,335,000	164,121,000
Interest rate swaps	3,529,000	4,941,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	6,985,000	6,284,000
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	67,466,000	61,969,000
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	34,634,000	30,601,000
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	16,007,000	14,896,000
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	54,243,000	50,371,000
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	179,335,000	164,121,000
Interest rate swaps	3,529,000	4,941,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	6,985,000	6,284,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	67,466,000	61,969,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	34,634,000	30,601,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	16,007,000	14,896,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	54,243,000	50,371,000
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