Note 9 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Assets Measured on Recurring Basis (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Available-for-sale securities	$ 81,943,424	$ 81,478,673
Interest Rate Swap [Member]
Interest Rate Swaps	1,833,515
Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	81,943,000	81,478,000
Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Interest Rate Swaps	1,834,000	568,000
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Interest Rate Swaps
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	81,943,000	81,478,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Interest Rate Swaps	1,834,000	568,000
Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	0
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member] | Interest Rate Swap [Member]
Interest Rate Swaps
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	32,965,370	33,898,458
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	32,965,000	33,898,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	32,965,000	33,898,000
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities
Corporate Debt Securities [Member]
Available-for-sale securities	3,060,791	3,065,000
Corporate Debt Securities [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	3,061,000	3,065,000
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	3,061,000	3,065,000
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	45,917,263	44,515,215
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	45,917,000	44,515,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities	45,917,000	44,515,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Available-for-sale securities