Note 11 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Financial Instruments (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Cash and cash equivalents	$ 1	$ 1
Held-to-maturity securities, approximate fair value	2	2
Federal Home Loan Bank stock	2	2
Mortgage loans held for sale	2	2
Loans, net	3	3
Interest receivable	2	2
Deposits	2	2
FHLB and Federal Reserve advances	2	2
Subordinated debentures	3	3
Interest payable	2	2
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	37,406,930	9,088,441
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Held-to-maturity securities, approximate fair value	16,457	27,528
Federal Home Loan Bank stock	4,597,500	4,611,000
Mortgage loans held for sale	1,921,819	2,183,633
Interest receivable	2,449,847	1,947,063
Deposits	607,364,350	505,362,750
FHLB and Federal Reserve advances	94,300,000	95,700,000
Interest payable	295,543	207,833
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net	629,605,009	538,273,640
Subordinated debentures	15,465,000	15,465,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	37,406,930	9,088,441
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Held-to-maturity securities, approximate fair value	16,729	28,153
Federal Home Loan Bank stock	4,597,500	4,611,000
Mortgage loans held for sale	1,921,819	2,183,633
Interest receivable	2,449,847	1,947,063
Deposits	606,548,280	504,829,161
FHLB and Federal Reserve advances	94,417,733	95,764,840
Interest payable	295,543	207,833
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net	627,498,508	537,645,692
Subordinated debentures	$ 15,465,000	$ 15,465,000