Note 13 - Fair Value of Financial Instruments - Fair Value Measurements, Recurring Basis (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Available For Sale ("AFS")	$ 531,421,573	$ 550,148,284
Taxable Municipal Bonds [Member]
Available For Sale ("AFS")	49,411,310	50,769,739
Collateralized Mortgage-Backed Securities [Member]
Available For Sale ("AFS")	332,117,548	319,281,268
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Student Loan Pools [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | SBA Bonds [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Tax Exempt Municipal Bonds [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Taxable Municipal Bonds [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Mortgage-Backed Securities [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Available For Sale ("AFS")	531,421,573	550,148,284
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Student Loan Pools [Member]
Available For Sale ("AFS")	52,494,121	59,156,982
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | SBA Bonds [Member]
Available For Sale ("AFS")	77,926,496	99,629,967
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Tax Exempt Municipal Bonds [Member]
Available For Sale ("AFS")	19,472,098	21,310,328
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Taxable Municipal Bonds [Member]
Available For Sale ("AFS")	49,411,310	50,769,739
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage-Backed Securities [Member]
Available For Sale ("AFS")	332,117,548	319,281,268
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Student Loan Pools [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | SBA Bonds [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Tax Exempt Municipal Bonds [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Taxable Municipal Bonds [Member]
Available For Sale ("AFS")	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized Mortgage-Backed Securities [Member]
Available For Sale ("AFS")	$ 0	$ 0