Note 3 - Loans and Allowance for Credit Losses (Details Textual) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Mar. 31, 2022	Jan. 01, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020	Aug. 08, 2020
Financing Receivable, before Allowance for Credit Loss, Total		$ 3,723,800,000		$ 3,723,800,000				$ 3,453,459,000
Increase (Decrease) in Finance Receivables				$ 270,000,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)				7.80%
Financing Receivable, Nonaccrual		1,787,000		$ 1,787,000
Financing Receivable, Nonaccrual, Interest Income		0	$ 0	0
Interest Lost on Nonaccrual Loans				100,000	$ 100,000
Financing Receivable, Accruing Trouble Debt Restructurings, Interest Income			400,000		800,000
Maximum [Member]
Interest Lost on Nonaccrual Loans		100,000	100,000
SBA, CARES Act, Paycheck Protection Program [Member]
Financing Receivable, before Allowance for Credit Loss, Total											$ 553,000,000
Financing Receivable With Less Than $0.1 Million Allowance [Member]
Financing Receivable, Nonaccrual		1,800,000		1,800,000
Commercial Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total		3,071,760,000		3,071,760,000				2,950,424,000
Financing Receivable Recorded Investment, Nonaccrual Status, Approximation		300,000		300,000
Financing Receivable, Nonaccrual		248,000		248,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[1]	1,187,650,000		1,187,650,000				1,137,419,000
Financing Receivable, Troubled Debt Restructuring		9,938,000	5,563,000	9,938,000	5,563,000	$ 2,829,000		4,973,000	$ 3,760,000	$ 6,414,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Grades 1-4 [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[2]	726,012,000		726,012,000				729,224,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | SBA, CARES Act, Paycheck Protection Program [Member]
Financing Receivable, before Allowance for Credit Loss, Total		2,900,000		2,900,000				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		2,900,000		2,900,000				40,100,000
Retail Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total		652,040,000		652,040,000				503,035,000
Financing Receivable, Nonaccrual		1,539,000		1,539,000
Retail Portfolio Segment [Member] | Home Equity Loan [Member]
Financing Receivable, before Allowance for Credit Loss, Total		33,300,000		33,300,000				29,500,000
Retail Portfolio Segment [Member] | Other Consumer Loans [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[3]	28,441,000		28,441,000				60,488,000
Financing Receivable, Troubled Debt Restructuring		3,000	1,396,000	3,000	1,396,000	13,000		1,202,000	1,099,000	1,146,000
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)
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Financing Receivable, before Allowance for Credit Loss, Total		623,599,000		623,599,000				442,547,000
Financing Receivable, Troubled Debt Restructuring		$ 2,339,000	$ 699,000	$ 2,339,000	$ 699,000	$ 2,346,000		$ 627,000	$ 820,000	$ 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, Troubled Debt Restructuring							$ 1,200,000

[1] For June 30, 2022, and December 31, 2021, includes $2.9 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 $33.3 million and $29.5 million as of June 30, 2022 and December 31, 2021, respectively.