Note 12 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Assets Measured on Recurring Basis (Details) - USD ($)	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017
Available-for-sale securities	$ 89,316,993	$ 81,478,673
US Government Corporations and Agencies Securities [Member]
Available-for-sale securities	5,548,134
US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities	31,870,512	33,898,458
Corporate Debt Securities [Member]
Available-for-sale securities	3,022,334	3,065,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities	48,876,013	44,515,215
Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities	$ 0
Fair Value, Measurements, Recurring [Member]
Available-for-sale securities		81,478,000	$ 89,317,000
Interest rate swaps		568,000	2,249,000
Fair Value, Measurements, Recurring [Member] | US Government Corporations and Agencies Securities [Member]
Available-for-sale securities			5,548,000
Fair Value, Measurements, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities		33,898,000	31,871,000
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Available-for-sale securities		3,065,000	3,022,000
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities		44,515,000	48,876,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available-for-sale securities
Interest rate swaps
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Government Corporations and Agencies Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available-for-sale securities		81,478,000	89,317,000
Interest rate swaps		568,000	2,249,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Government Corporations and Agencies Securities [Member]
Available-for-sale securities			5,548,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities		33,898,000	31,871,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities		3,065,000	3,022,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities		44,515,000	48,876,000
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available-for-sale securities
Interest rate swaps
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Government Corporations and Agencies Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US States and Political Subdivisions Debt Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Available-for-sale securities
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available-for-sale securities