Note 19 - Fair Values of Financial Instruments - Fair Value by Balance Sheet Grouping (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Financial assets:
Available-for-sale securities, at fair value	$ 24,399,881	$ 31,499,132
Reported Value Measurement [Member]
Financial assets:
Cash and due from banks	4,988,000	4,766,000
Interest-bearing deposits with banks	4,885,000	11,645,000
Available-for-sale securities, at fair value	24,400,000	31,499,000
Loans held for sale	15,424,000	14,221,000
Loans held for investment, net	257,896,000	241,399,000
Stock in financial institutions	3,826,000	3,575,000
Financial liabilities:
Demand deposits, savings and NOW deposits	172,512,000	160,961,000
Time deposits	63,049,000	63,561,000
Federal Home Loan Bank advances	45,000,000	50,000,000
Estimate of Fair Value Measurement [Member]
Financial assets:
Cash and due from banks	4,988,000	4,766,000
Interest-bearing deposits with banks	4,885,000	11,645,000
Available-for-sale securities, at fair value	24,400,000	31,499,000
Loans held for sale	15,424,000	14,221,000
Loans held for investment, net	257,937,000	241,440,000
Stock in financial institutions	3,826,000	3,575,000
Financial liabilities:
Demand deposits, savings and NOW deposits	168,080,000	156,529,000
Time deposits	63,076,000	63,588,000
Federal Home Loan Bank advances	45,176,000	50,176,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets:
Cash and due from banks	4,988,000	4,766,000
Interest-bearing deposits with banks	4,885,000	11,645,000
Available-for-sale securities, at fair value	0	0
Loans held for sale	0	0
Loans held for investment, net	0	0
Stock in financial institutions	0	0
Financial liabilities:
Demand deposits, savings and NOW deposits	168,080,000	156,529,000
Time deposits	0	0
Federal Home Loan Bank advances	0	0
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets:
Cash and due from banks	0	0
Interest-bearing deposits with banks	0	0
Available-for-sale securities, at fair value	24,400,000	31,499,000
Loans held for sale	15,424,000	14,221,000
Loans held for investment, net	0	0
Stock in financial institutions	3,826,000	3,575,000
Financial liabilities:
Demand deposits, savings and NOW deposits	0	0
Time deposits	63,076,000	63,588,000
Federal Home Loan Bank advances	45,176,000	50,176,000
Estimate of Fair Value Measurement [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets:
Cash and due from banks	0	0
Interest-bearing deposits with banks	0	0
Available-for-sale securities, at fair value	0	0
Loans held for sale	0	0
Loans held for investment, net	257,937,000	241,440,000
Stock in financial institutions	0	0
Financial liabilities:
Demand deposits, savings and NOW deposits	0	0
Time deposits	0	0
Federal Home Loan Bank advances	$ 0	$ 0