Note 13 - Disclosures About Fair Value of Assets and Liabilities - Fair Value of Financial Instruments (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Interest-bearing time deposits at other financial institutions	$ 250,000	$ 250,000
Reported Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	86,421,380	34,121,642
Reported Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Interest-bearing time deposits at other financial institutions	250,000	250,000
Federal Home Loan Bank stock	3,157,500	5,387,200
Mortgage loans held for sale	944,969	1,516,849
Interest receivable	3,475,749	3,390,944
Deposits	839,988,502	749,618,822
Federal Home Loan Bank advances	50,000,000	105,300,000
Interest payable	832,494	821,811
Reported Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net	744,022,856	778,298,606
Subordinated debentures	15,465,000	21,760,829
Note payable to Bank	11,200,000	5,000,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Cash and cash equivalents	86,421,380	34,121,642
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Interest-bearing time deposits at other financial institutions	250,265	250,116
Federal Home Loan Bank stock	3,157,500	5,387,200
Mortgage loans held for sale	944,969	1,516,849
Interest receivable	3,475,749	3,390,944
Deposits	840,446,988	747,903,071
Federal Home Loan Bank advances	50,011,559	105,325,386
Interest payable	832,494	821,811
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Loans, net	752,524,071	783,910,789
Subordinated debentures	15,465,000	21,760,829
Note payable to Bank	$ 11,200,000	$ 5,000,000