Note 3 - Loans and Allowance for Credit Losses (Details Textual)		3 Months Ended		9 Months Ended
		Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jan. 01, 2022 USD ($)	Dec. 31, 2021 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Aug. 08, 2020 USD ($)
Financing Receivable, before Allowance for Credit Loss, Total		$ 3,880,958,000		$ 3,880,958,000				$ 3,453,459,000
Increase (Decrease) in Finance Receivables				$ 427,000,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)				12.40%
Financing Receivable, Allowance for Credit Loss, Ending Balance		39,120,000	$ 37,423,000	$ 39,120,000	$ 37,423,000	$ 35,974,000		35,363,000	$ 35,913,000	$ 37,967,000
Financing Receivable, Nonaccrual, Interest Income		$ 0	0	0	0
Interest Lost on Nonaccrual Loans			100,000	$ 100,000	100,000
Financing Receivable, Accruing Trouble Debt Restructurings, Interest Income			$ 400,000		$ 1,200,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts		0	1	0	1
Financing Receivable, Troubled Debt Restructuring, Subsequent Default			$ 100,000		$ 100,000
Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss, Ending Balance							$ (400,000)	(400,000)
Maximum [Member]
Interest Lost on Nonaccrual Loans			100,000
Collateral Dependent Loans [Member]
Financing Receivable, before Allowance for Credit Loss, Total		$ 1,400,000		$ 1,400,000
SBA, CARES Act, Paycheck Protection Program [Member]
Financing Receivable, before Allowance for Credit Loss, Total											$ 553,000,000
Nonaccrual Loans [Member]
Financing Receivable, Allowance for Credit Loss, Ending Balance		100,000		100,000
Commercial Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total		3,145,063,000		3,145,063,000				2,950,424,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[1]	1,213,630,000		1,213,630,000				1,137,419,000
Financing Receivable, Allowance for Credit Loss, Ending Balance		9,740,000	10,178,000	9,740,000	10,178,000	8,608,000		10,782,000	9,340,000	9,424,000
Financing Receivable, Troubled Debt Restructuring		9,066,000	5,655,000	9,066,000	5,655,000	9,938,000		4,973,000	5,563,000	6,414,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss, Ending Balance								(1,571,000)
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Grades 1-4 [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[2]	740,682,000		740,682,000				729,224,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Non-real Estate Business Assets [Member]
Financing Receivable, Collateral Dependent Loans		200,000		200,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | SBA, CARES Act, Paycheck Protection Program [Member]
Financing Receivable, before Allowance for Credit Loss, Total		2,600,000		2,600,000				40,100,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | SBA, CARES Act, Paycheck Protection Program [Member] | Grades 1-4 [Member]
Financing Receivable, before Allowance for Credit Loss, Total		2,600,000		2,600,000				40,100,000
Retail Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total		735,895,000		735,895,000				503,035,000
Retail Portfolio Segment [Member] | Home Equity Loan [Member]
Financing Receivable, before Allowance for Credit Loss, Total		35,600,000		35,600,000				29,500,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Financing Receivable, before Allowance for Credit Loss, Total		705,441,000		705,441,000				442,547,000
Financing Receivable, Allowance for Credit Loss, Ending Balance		11,951,000	3,059,000	11,951,000	3,059,000	10,267,000		2,449,000	2,894,000	3,240,000
Financing Receivable, Troubled Debt Restructuring		2,544,000	$ 648,000	2,544,000	$ 648,000	2,339,000		627,000	$ 699,000	$ 806,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member]
Financing Receivable, Allowance for Credit Loss, Ending Balance								5,395,000
Financing Receivable, Troubled Debt Restructuring							1,200,000
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member] | Residential Real Estate [Member]
Financing Receivable, Collateral Dependent Loans		1,200,000		1,200,000
Retail Portfolio Segment [Member] | Other Consumer Loans [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[3]	30,454,000		30,454,000				60,488,000
Financing Receivable, Troubled Debt Restructuring		$ 2,000		$ 2,000		$ 3,000		$ 1,202,000
Retail Portfolio Segment [Member] | Other Consumer Loans [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | Accounting Standards Update 2016-13 [Member]
Financing Receivable, Troubled Debt Restructuring							$ (1,200,000)

[1] For September 30, 2022, and December 31, 2021, includes $2.6 million and $40.1 million in loans originated under the Paycheck Protection Program, respectively.

[2] Included in Commercial and Industrial Loans Grades 1 – 4 are $40.1 million of loans originated under the Paycheck Protection Program.

[3] In conjunction with the adoption of the CECL methodology effective January 1, 2022, home equity lines of credit were reclassified to 1-4 family mortgage loans from other consumer loans. Home equity lines of credit totaled $35.6 million and $29.5 million as of September 30, 2022 and December 31, 2021, respectively.