Note 3 - Loans Held for Investment, Net - Impaired Loans (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Impaired loans, with no related allowance recorded, recorded investment	$ 3,605,635	$ 3,643,608
Impaired loans, with no related allowance recorded, principal net of charge-offs,	3,605,635	3,643,608
Impaired loans, with no related allowance recorded, average recorded investment	3,623,202	3,663,931
Impaired loans, with an allowance recorded, recorded investment	0	0
Impaired loans, with an allowance recorded, principal net of charge-offs	0	0
Impaired loans, related allowance	0	0
Impaired loans, with an allowance recorded, average recorded investment	0	0
Impaired loans, fair value disclosure	3,605,635	3,643,608
Impaired loans, principal net of charge-offs	3,605,635	3,643,608
Impaired loans, average recorded investment	3,623,202	3,663,931
Commercial Real Estate Portfolio Segment [Member]
Impaired loans, with no related allowance recorded, recorded investment	2,988,885	2,993,923
Impaired loans, with no related allowance recorded, principal net of charge-offs,	2,988,885	2,993,923
Impaired loans, with no related allowance recorded, average recorded investment	2,999,285	3,007,495
Impaired loans, related allowance	0	0
Impaired loans, fair value disclosure	2,988,885	2,993,923
Impaired loans, principal net of charge-offs	2,988,885	2,993,923
Impaired loans, average recorded investment	2,999,285	3,007,495
One-to-four Family Residential Real Estate Portfolio Segment [Member]
Impaired loans, with no related allowance recorded, recorded investment	616,750	649,685
Impaired loans, with no related allowance recorded, principal net of charge-offs,	616,750	649,685
Impaired loans, with no related allowance recorded, average recorded investment	623,917	656,436
Impaired loans, related allowance	0	0
Impaired loans, fair value disclosure	616,750	649,685
Impaired loans, principal net of charge-offs	616,750	649,685
Impaired loans, average recorded investment	623,917	656,436
Commercial and Industrial Portfolio Segment [Member]
Impaired loans, with no related allowance recorded, recorded investment
Impaired loans, with no related allowance recorded, principal net of charge-offs,
Impaired loans, with no related allowance recorded, average recorded investment
Impaired loans, related allowance	0	0
Impaired loans, fair value disclosure
Impaired loans, principal net of charge-offs
Impaired loans, average recorded investment
Consumer and Other Portfolio Segment [Member]
Impaired loans, with no related allowance recorded, recorded investment	0	0
Impaired loans, with no related allowance recorded, principal net of charge-offs,	0	0
Impaired loans, with no related allowance recorded, average recorded investment	0	0
Impaired loans, related allowance	0	0
Impaired loans, fair value disclosure	0	0
Impaired loans, principal net of charge-offs	0	0
Impaired loans, average recorded investment	$ 0	$ 0