Note 3 - Loans and Allowance for Credit Losses (Details Textual) - USD ($)		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021	Jan. 01, 2022	Dec. 31, 2021	Dec. 31, 2020	Aug. 08, 2020
Financing Receivable, before Allowance for Credit Loss, Total		$ 3,555,790,000			$ 3,453,459,000
Increase (Decrease) in Finance Receivables		$ 102,000,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)		3.00%
Financing Receivable, Nonaccrual, Interest Income		$ 0	$ 0
Financing Receivable, Nonaccrual		1,612,000
Financing Receivable, Accruing Trouble Debt Restructurings, Interest Income			400,000
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 No Allowance [Member]
Financing Receivable, Nonaccrual		1,500,000
Commercial Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total		3,004,562,000			2,950,424,000
Financing Receivable, Nonaccrual		0
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[1]	1,153,814,000			1,137,419,000
Financing Receivable, Troubled Debt Restructuring		2,829,000	3,760,000		4,973,000	$ 6,414,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | Grades 1-4 [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[2]	719,267,000			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		12,200,000			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		12,200,000			40,100,000
Retail Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss, Total		551,228,000			503,035,000
Financing Receivable, Nonaccrual		1,612,000
Retail Portfolio Segment [Member] | Home Equity Loan [Member]
Financing Receivable, before Allowance for Credit Loss, Total		31,900,000			29,500,000
Retail Portfolio Segment [Member] | Other Consumer Loans [Member]
Financing Receivable, before Allowance for Credit Loss, Total	[3]	28,672,000			60,488,000
Financing Receivable, Troubled Debt Restructuring		13,000	1,099,000		1,202,000	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		522,556,000			442,547,000
Financing Receivable, Troubled Debt Restructuring		$ 2,346,000	$ 820,000		$ 627,000	$ 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 March 31, 2022, and December 31, 2021, includes $12.2 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 $12.2 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 $31.9 million and $29.5 million as of March 31, 2022 and December 31, 2021, respectively.