Note 13 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Assets Measured on Recurring Basis (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Available-for-sale securities	$ 140,009,454	$ 118,245,314
US Government Agencies Debt Securities [Member]
Available-for-sale securities	2,515,340	2,487,793
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	45,048,037	36,174,727
Corporate Debt Securities [Member]
Available-for-sale securities	21,540,987	15,535,187
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	13,560,632	13,811,371
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	57,344,458	50,236,236
Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	0
Fair Value, Recurring [Member]
Available-for-sale securities	140,009,000	118,245,000
Interest rate swaps	5,231,000	1,628,000
Fair Value, Recurring [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	2,515,000	2,488
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	45,048,000	36,175,000
Fair Value, Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	21,541,000	15,535,000
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities	13,561,000	13,811
Fair Value, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	57,344,000	50,236,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities
Interest rate swaps
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	140,009,000	118,245,000
Interest rate swaps	5,231,000	1,628,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities	2,515,000	2,488
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	45,048,000	36,175,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities	21,541,000	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	13,561,000	13,811
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	57,344,000	50,236,000
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities
Interest rate swaps
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Agencies Debt Securities [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Available-for-sale securities
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities