Note 5 - Fair Value Measurements - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Available for sale securities	$ 788,910	$ 786,438
US Treasury Securities [Member]
Available for sale securities	205,513	207,597
US Government Agencies Debt Securities [Member]
Available for sale securities	102,649	100,933
Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available for sale securities	114,126	116,741
US States and Political Subdivisions Debt Securities [Member]
Available for sale securities	291,860	286,003
Corporate Debt Securities [Member]
Available for sale securities	74,762	75,164
Fair Value, Recurring [Member]
Loans receivable	8,596	8,494
Interest rate swaps, Fair value	901
Derivative financial instruments		1,096
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Loans receivable	0	0
Interest rate swaps, Fair value	0
Derivative financial instruments		0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Loans receivable	8,596	8,494
Interest rate swaps, Fair value	901
Derivative financial instruments		1,096
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Loans receivable	0	0
Interest rate swaps, Fair value	0
Derivative financial instruments		0
Fair Value, Recurring [Member] \| US Treasury Securities [Member]
Available for sale securities	205,513	207,597
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Available for sale securities	205,513	207,597
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| US Treasury Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member]
Available for sale securities	102,649	100,933
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Available for sale securities	102,649	100,933
Fair Value, Recurring [Member] \| US Government Agencies Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member]
Available for sale securities	114,126	116,741
Fair Value, Recurring [Member] \| Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Inputs, Level 1 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Inputs, Level 2 [Member]
Available for sale securities	114,126	116,741
Fair Value, Recurring [Member] \| Mortgage-Backed Securities, Issued by US Government Sponsored Enterprises [Member] \| Fair Value, Inputs, Level 3 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member]
Available for sale securities	291,860	286,003
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Available for sale securities	291,860	286,003
Fair Value, Recurring [Member] \| US States and Political Subdivisions Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Available for sale securities	74,762	75,164
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Available for sale securities	0	0
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Available for sale securities	74,762	75,164
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Available for sale securities	$ 0	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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