Note 3 - Loans and Allowance for Credit Losses (Details Textual)		3 Months Ended		12 Months Ended
		Mar. 31, 2023 USD ($)	Mar. 31, 2022 USD ($)	Dec. 31, 2022 USD ($)	Jan. 01, 2022 USD ($)	Dec. 31, 2021 USD ($)
Financing Receivable, before Allowance for Credit Loss		$ 3,965,528,000		$ 3,916,619,000
Increase (Decrease) in Finance Receivables		$ 48,900,000
Loans and Leases Receivable, Percentage Period Increase (Decrease)		1.20%
Financing Receivable, Nonaccrual, Interest Income		$ 0		0
Financing Receivable, Revolving, Converted to Term Loan		$ 0		0
Financing Receivable, Modified, Number of Contracts		0	2
Collateral Dependent Loans [Member]
Financing Receivable, before Allowance for Credit Loss		$ 7,800,000		7,700,000
Commercial Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss		3,140,420,000		3,131,830,000
Financing Receivable, Modified, Number of Contracts			0
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member]
Financing Receivable, before Allowance for Credit Loss	[1]	1,173,440,000		1,185,083,000
Financing Receivable, Modified, Number of Contracts			0
Financing Receivable, Troubled Debt Restructuring			$ 2,829,000			$ 4,973,000
Commercial Portfolio Segment [Member] | Commercial and Industrial [Member] | SBA, CARES Act, Paycheck Protection Program [Member]
Financing Receivable, before Allowance for Credit Loss		400,000		900,000
Retail Portfolio Segment [Member]
Financing Receivable, before Allowance for Credit Loss		825,108,000		784,789,000
Financing Receivable, Modified, Number of Contracts			2
Retail Portfolio Segment [Member] | Other Consumer Loans [Member]
Financing Receivable, before Allowance for Credit Loss		30,101,000		29,753,000
Financing Receivable, Modified, Number of Contracts			0
Financing Receivable, Troubled Debt Restructuring			$ 13,000			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)
Retail Portfolio Segment [Member] | One to Four Family Mortgages [Member]
Financing Receivable, before Allowance for Credit Loss		$ 795,007,000		$ 755,036,000
Financing Receivable, Modified, Number of Contracts			2
Financing Receivable, Troubled Debt Restructuring			$ 2,346,000			$ 627,000
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, 2023, and December 31, 2022, includes $0.4 million and $0.9 million in loans originated under the Paycheck Protection Program, respectively.