Note 3 - Loans Held for Investment, Net - Impaired Loans (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Impaired loans, with no related allowance recorded, recorded investment	$ 5,144,627	$ 5,436,972
Impaired loans, with no related allowance recorded, principal net of charge-offs	5,144,627	5,436,972
Impaired loans, with no related allowance recorded, average recorded investment	5,240,771	5,503,793
Impaired loans, with an allowance recorded, recorded investment	550,000	0
Impaired loans, with an allowance recorded, principal net of charge-offs	550,000	0
Impaired loans, related allowance	215,000	0
Impaired loans, with an allowance recorded, average recorded investment	550,000	0
Impaired loans, recorded investment	5,694,627	5,436,972
Impaired loans, principal net of charge-offs	5,694,627	5,436,972
Impaired loans, average recorded investment	5,790,771	5,503,793
Impaired loans, fair value disclosure	5,694,627	5,436,972
Commercial Real Estate Portfolio Segment [Member]
Impaired loans, with no related allowance recorded, recorded investment	3,159,122	3,483,078
Impaired loans, with no related allowance recorded, principal net of charge-offs	3,159,122	3,483,078
Impaired loans, with no related allowance recorded, average recorded investment	3,196,492	3,521,421
Impaired loans, related allowance	215,000	0
Impaired loans, recorded investment	3,709,122	3,483,078
Impaired loans, principal net of charge-offs	3,709,122	3,483,078
Impaired loans, average recorded investment	3,746,492	3,521,421
Impaired loans, fair value disclosure	3,709,122	3,483,078
One-to-four Family Residential Real Estate Portfolio Segment [Member]
Impaired loans, with no related allowance recorded, recorded investment	710,795	679,184
Impaired loans, with no related allowance recorded, principal net of charge-offs	710,795	679,184
Impaired loans, with no related allowance recorded, average recorded investment	746,539	684,632
Impaired loans, related allowance	0	0
Impaired loans, recorded investment	710,795	679,184
Impaired loans, principal net of charge-offs	710,795	679,184
Impaired loans, average recorded investment	746,539	684,632
Impaired loans, fair value disclosure	710,795	679,184
Commercial and Industrial Portfolio Segment [Member]
Impaired loans, with no related allowance recorded, recorded investment	1,274,710	1,274,710
Impaired loans, with no related allowance recorded, principal net of charge-offs	1,274,710	1,274,710
Impaired loans, with no related allowance recorded, average recorded investment	1,297,740	1,297,740
Impaired loans, related allowance	0	0
Impaired loans, recorded investment	1,274,710	1,274,710
Impaired loans, principal net of charge-offs	1,274,710	1,274,710
Impaired loans, average recorded investment	1,297,740	1,297,740
Impaired loans, fair value disclosure	1,274,710	1,274,710
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, recorded investment	0	0
Impaired loans, principal net of charge-offs	0	0
Impaired loans, average recorded investment	0	0
Impaired loans, fair value disclosure	$ 0	$ 0