Note 9 - Fair Value Measurement - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Estimated fair value	$ 484,416	$ 444,703
US Treasury Securities [Member]
Estimated fair value	9,770	9,707
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Estimated fair value	236,725	214,408
Commercial Mortgage Backed Securities Issued by US Government Agencies [Member]
Estimated fair value	110,661	99,581
US States and Political Subdivisions Debt Securities [Member]
Estimated fair value	127,260	121,007
Fair Value, Recurring [Member]
Estimated fair value	484,416	446,705
Fair Value, Recurring [Member] | Interest Rate Swap [Member]
Interest rate swaps		2,002
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	484,416	446,705
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]
Interest rate swaps		2,002
Fair Value, Recurring [Member] | US Treasury Securities [Member]
Estimated fair value	9,770	9,707
Fair Value, Recurring [Member] | US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	9,770	9,707
Fair Value, Recurring [Member] | Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Estimated fair value	236,725	214,408
Fair Value, Recurring [Member] | Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	236,725	214,408
Fair Value, Recurring [Member] | Commercial Mortgage Backed Securities Issued by US Government Agencies [Member]
Estimated fair value	110,661	99,581
Fair Value, Recurring [Member] | Commercial Mortgage Backed Securities Issued by US Government Agencies [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	110,661	99,581
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member]
Estimated fair value	127,260	121,007
Fair Value, Recurring [Member] | US States and Political Subdivisions Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Estimated fair value	$ 127,260	$ 121,007