Note 6 - Investments, Available for Sale ("AFS") (Details Textual)	6 Months Ended
	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-Sale, Amortized Cost	$ 594,620,986		$ 604,157,308
Debt Securities, Available-for-Sale	541,952,626		$ 550,148,284
Debt Securities, Available-for-Sale, Allowance for Credit Loss	0
Proceeds from Sale of Debt Securities, Available-for-Sale	0	$ 0
Debt Securities, Available-for-Sale, Gain (Loss)	$ 0	$ 0
Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions	427		416
Debt Securities, Available-for-Sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions	356		211
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss	$ 2,800,000
Asset Pledged as Collateral [Member] | Deposit Accounts, FHLB Advances and Other Borrowings [Member]
Debt Securities, Available-for-Sale, Amortized Cost	362,800,000		$ 318,000,000.0
Debt Securities, Available-for-Sale	332,500,000		297,000,000.0
Mortgage-Backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-Sale, Amortized Cost	79,000,000.0		60,100,000
Debt Securities, Available-for-Sale	$ 72,000,000.0		$ 53,800,000