Note 11 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Assets Measured on Recurring Basis (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale securities	$ 81,478,673	$ 92,399,235
Interest Rate Swap [Member]
Interest Rate Swaps	567,704
Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities
Fair Value, Inputs, Level 1 [Member] | Interest Rate Swap [Member]
Interest Rate Swaps
Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	81,478,000	92,399,000
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Interest Rate Swaps	568,000
Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities
Fair Value, Inputs, Level 3 [Member] | Interest Rate Swap [Member]
Interest Rate Swaps
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	33,898,458	38,337,525
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	33,898,000	38,338,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities
Corporate Debt Securities [Member]
Available-for-sale securities	3,065,000	7,053,522
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	3,065,000	7,053,000
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	44,515,215	47,008,188
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities	44,515,000	47,008,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities