Note 4 - Loans and Allowance for Credit Losses on Loans (Details Textual) Pure in Thousands		3 Months Ended
		Mar. 31, 2022 USD ($)	Mar. 31, 2021 USD ($)	Mar. 07, 2022 USD ($)	Dec. 31, 2021 USD ($)
Financing Receivable, Accrued Interest, after Allowance for Credit Loss		$ 12,000,000			$ 11,000,000
Loans and Leases Receivable, Net of Deferred Income	[1],[2]	4,847,683,000			4,169,303,000
Loans and Leases Receivable, Related Parties, Ending Balance		65,000,000			54,000,000
Financing Receivable, Purchased with Credit Deterioration, Interest Income		459,000	$ 0
Financing Receivable, Nonaccrual, Interest Income		$ 0	$ 0
Financing Receivable, Modifications, Number of Contracts		0	0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts		0	0
Mortgage Loans in Process of Foreclosure, Amount		$ 1,200,000			917,000
Asset Pledged as Collateral [Member] | Federal Home Loan Bank Advances [Member]
Loans and Leases Receivable, Net of Deferred Income		$ 2,700,000,000			$ 2,200,000,000
Commonwealth [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans, Gross				$ 632,404,000

[1] Pursuant to the CARES Act, loan deferrals granted to borrowers experiencing business interruptions related to the pandemic were not classified as TDRs and not included in past due and/or non-performing loan statistics. As of March 31, 2022 and December 31, 2021, outstanding CARES Act loan deferrals of $165,000 and $169,000 are reflected as current, respectively.

[2] Total loans are presented inclusive of premiums, discounts and net loan origination fees and costs.