Note 7 - Fair Values of Financial Instruments - Significant Unobservable Inputs (Details)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Impaired loans, fair value disclosure	$ 5,694,627	$ 5,436,972
Commercial Real Estate Portfolio Segment [Member]
Impaired loans, fair value disclosure	3,709,122	3,483,078
One-to-four Family Residential Real Estate Portfolio Segment [Member]
Impaired loans, fair value disclosure	710,795	679,184
Commercial and Industrial Portfolio Segment [Member]
Impaired loans, fair value disclosure	1,274,710	1,274,710
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Impaired loans, fair value disclosure	5,479,627	5,436,972
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Commercial Real Estate Portfolio Segment [Member]
Impaired loans, fair value disclosure	$ 3,494,122	$ 3,483,078
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Commercial Real Estate Portfolio Segment [Member] | Minimum [Member] | Measurement Input, Discount Rate [Member]
Unobservable input valuation	17	17
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Commercial Real Estate Portfolio Segment [Member] | Maximum [Member] | Measurement Input, Discount Rate [Member]
Unobservable input valuation	18	18
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | One-to-four Family Residential Real Estate Portfolio Segment [Member]
Impaired loans, fair value disclosure	$ 710,795	$ 679,184
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | One-to-four Family Residential Real Estate Portfolio Segment [Member] | Minimum [Member] | Measurement Input, Discount Rate [Member]
Unobservable input valuation	17	17
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | One-to-four Family Residential Real Estate Portfolio Segment [Member] | Maximum [Member] | Measurement Input, Discount Rate [Member]
Unobservable input valuation	18	18
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Commercial and Industrial Portfolio Segment [Member]
Impaired loans, fair value disclosure	$ 1,274,710	$ 1,274,710
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Commercial and Industrial Portfolio Segment [Member] | Minimum [Member] | Measurement Input, Discount Rate [Member]
Unobservable input valuation	17	17
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Valuation, Market Approach [Member] | Commercial and Industrial Portfolio Segment [Member] | Maximum [Member] | Measurement Input, Discount Rate [Member]
Unobservable input valuation	18	18