Note 17 - Financial Assets Measured at Fair Value on a Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	$ 546,525	$ 692,360
Equity securities	12,056	12,410
US Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	301
US Government Agencies Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	86,709	97,499
US States and Political Subdivisions Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	95,367	131,035
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	256,161	329,938
Collateralized Mortgage Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	101,672	127,012
Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	6,315	6,876
Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Equity securities	12,056	12,410
Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	546,472	692,285
Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	301
Fair Value, Inputs, Level 2 [Member] | US Government Agencies Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	86,709	97,499
Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	95,367	131,035
Fair Value, Inputs, Level 2 [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	256,161	329,938
Fair Value, Inputs, Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	101,672	127,012
Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	6,262	6,801
Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	53	75
Fair Value, Inputs, Level 3 [Member] | Corporate Debt Securities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasuries	53	75
Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	558,581	704,770
Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	12,056	12,410
Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	546,472	692,285
Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	53	75
Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	3,929	4,803
Nonrecurring [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	3,928	4,686
Nonrecurring [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	1	117
Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	3,929	4,803
Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	3,928	4,686
Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member] | Mortgage Servicing Rights [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Asset fair value measurements	$ 1	$ 117