Note 3 - Available-for-sale Securities (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Available-for-sale Securities, Greater than 10% of Stockholders' Equity	$ 0	$ 0
Available-for-sale Securities	24,399,881	31,499,132
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	0
Loans and Securities Pledged to Secure FHLB Advances	137,900,000
Loans and Securities Pledged to Secure Public Deposits	4,400,000
Single Family Mortgage Loans [Member]
Available-for-sale Securities	10,000,000	10,100,000
Commercial Mortgage Backed Securities [Member]
Available-for-sale Securities	$ 0	$ 0