Note 7 - Loans and the Allowance for Loan Losses - Past Due Loans Receivable (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Loans	$ 4,992,785,000	$ 4,606,176,000
Recorded investment over 90 days past due and still accruing	127,000	335,000
Financial Asset, 30 to 59 Days Past Due [Member]
Loans	3,692,000	4,879,000
Financial Asset, 60 to 89 Days Past Due [Member]
Loans	3,386,000	2,636,000
Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	12,020,000	6,468,000
Financial Asset, Past Due [Member]
Loans	19,098,000	13,983,000
Financial Asset, Not Past Due [Member]
Loans	4,973,687,000	4,592,193,000
Commercial Real Estate Portfolio Segment [Member]
Loans	3,570,120,000	3,398,858,000
Recorded investment over 90 days past due and still accruing	64,000	98,000
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	2,311,000	3,401,000
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	3,063,000	674,000
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	10,210,000	4,100,000
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	15,584,000	8,175,000
Commercial Real Estate Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	3,554,536,000	3,390,683,000
Commercial Real Estate Portfolio Segment [Member] | Commercial [Member]
Loans	2,217,928,000	2,020,406,000
Recorded investment over 90 days past due and still accruing	44,000	98,000
Commercial Real Estate Portfolio Segment [Member] | Commercial [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	240,000	1,491,000
Commercial Real Estate Portfolio Segment [Member] | Commercial [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	536,000	210,000
Commercial Real Estate Portfolio Segment [Member] | Commercial [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	2,954,000	1,681,000
Commercial Real Estate Portfolio Segment [Member] | Commercial [Member] | Financial Asset, Past Due [Member]
Loans	3,730,000	3,382,000
Commercial Real Estate Portfolio Segment [Member] | Commercial [Member] | Financial Asset, Not Past Due [Member]
Loans	2,214,198,000	2,017,024,000
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Loans	669,798,000	722,074,000
Recorded investment over 90 days past due and still accruing	0	0
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	279,000	320,000
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	1,320,000	41,000
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	3,198,000	638,000
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Financial Asset, Past Due [Member]
Loans	4,797,000	999,000
Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member] | Financial Asset, Not Past Due [Member]
Loans	665,001,000	721,075,000
Commercial Real Estate Portfolio Segment [Member] | Residential [Member]
Loans	682,394,000	656,378,000
Recorded investment over 90 days past due and still accruing	20,000	0
Commercial Real Estate Portfolio Segment [Member] | Residential [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	1,792,000	1,590,000
Commercial Real Estate Portfolio Segment [Member] | Residential [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	1,207,000	423,000
Commercial Real Estate Portfolio Segment [Member] | Residential [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	4,058,000	1,781,000
Commercial Real Estate Portfolio Segment [Member] | Residential [Member] | Financial Asset, Past Due [Member]
Loans	7,057,000	3,794,000
Commercial Real Estate Portfolio Segment [Member] | Residential [Member] | Financial Asset, Not Past Due [Member]
Loans	675,337,000	652,584,000
Commercial Portfolio Segment [Member]
Loans	1,358,838,000	1,153,873,000
Recorded investment over 90 days past due and still accruing	52,000	222,000
Commercial Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	1,101,000	1,183,000
Commercial Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	71,000	1,934,000
Commercial Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	1,622,000	2,186,000
Commercial Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	2,794,000	5,303,000
Commercial Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	1,356,044,000	1,148,570,000
Consumer Portfolio Segment [Member]
Loans	63,827,000	53,445,000
Recorded investment over 90 days past due and still accruing	11,000	15,000
Consumer Portfolio Segment [Member] | Financial Asset, 30 to 59 Days Past Due [Member]
Loans	280,000	295,000
Consumer Portfolio Segment [Member] | Financial Asset, 60 to 89 Days Past Due [Member]
Loans	252,000	28,000
Consumer Portfolio Segment [Member] | Financial Asset, Equal to or Greater than 90 Days Past Due [Member]
Loans	188,000	182,000
Consumer Portfolio Segment [Member] | Financial Asset, Past Due [Member]
Loans	720,000	505,000
Consumer Portfolio Segment [Member] | Financial Asset, Not Past Due [Member]
Loans	$ 63,107,000	$ 52,940,000