Note 4 - Loans (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Servicing Asset, Total	$ 141,200,000
Impaired Financing Receivable, Recorded Investment, Total	65,846,000	$ 95,405,000
Impaired Financing Receivable, Average Recorded Investment, Total	72,740,000	91,353,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	$ 1,074,000	$ 2,394,000
Percentage Of Charge Off To Contractual Balances For Impaired Loans	10.70%	7.10%
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	$ 0	$ 0	$ 2,190,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	0
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	0
Loans and Leases Receivable, Gross, Total	16,342,479,000	15,644,396,000
Loans and Leases Receivable, Allowance, Ending Balance	$ 136,157,000	166,538,000
SBA's Paycheck Protection Program [Member]
Financing Receivable, Number of Contracts	671
Loans and Leases Receivable, Gross, Total	$ 90,500,000
Loans and Leases Receivable, Forgiven	337,000,000.0
Loans and Leases Receivable, Allowance, Ending Balance	$ 0
Minimum [Member]
Period Loan Is In Payment Default (Day)	60 days
Maximum [Member]
Period Loan Is In Payment Default (Day)	90 days
Nonaccrual Loans [Member]
Impaired Financing Receivable, Recorded Investment, Total	$ 65,800,000	67,700,000
Accruing Troubled Debt Restructuring [Member]
Impaired Financing Receivable, Recorded Investment, Total		27,700,000
Financing Receivable, Troubled Debt Restructuring	12,800,000	27,700,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	7,000	122,000
Non-accruing Troubled Debt Restructuring [Member]
Financing Receivable, Troubled Debt Restructuring	8,200,000	9,000,000.0
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	3,000	24,000
Residential Portfolio Segment [Member]
Servicing Asset, Total	92,100,000
Repossessed Assets, Total	2,000.0	808,000
Loans and Leases Receivable, Gross, Total	4,182,006,000	4,145,389,000
Commercial Real Estate Portfolio Segment [Member]
Servicing Asset, Total	17,000,000.0
Impaired Financing Receivable, Average Recorded Investment, Total	38,047,000	41,649,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	1,044,000	1,602,000
Loans and Leases Receivable, Gross, Total	$ 8,143,272,000	7,555,027,000
Loans and Leases Receivable, Allowance, Ending Balance		49,205,000
Financing Receivable, Number of Contracts with Approved Forbearance Requests	7
Loans and Leases Receivable with Approved Forbearance Requests, Gross	$ 49,400,000
Financing Receivable with Modifications, Percentage of Total Commercial Real Estate Loans	0.60%
Commercial Construction Loans [Member]
Servicing Asset, Total	$ 30,100,000
Commercial Portfolio Segment [Member]
Servicing Asset, Total	2,300,000
Impaired Financing Receivable, Average Recorded Investment, Total	21,453,000	31,009,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	0	246,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	0	0	$ 2,190,000
Loans and Leases Receivable, Gross, Total	$ 2,982,399,000	2,836,833,000
Loans and Leases Receivable, Allowance, Ending Balance		68,742,000
Financing Receivable, Number of Contracts with Approved Forbearance Requests	4
Loans and Leases Receivable with Approved Forbearance Requests, Gross	$ 20,500,000
Financing Receivable with Modifications, Percentage of Total Commercial Real Estate Loans	0.70%
Real Estate Loan [Member]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	$ 11,500,000	11,200,000,000
Commercial Loans [Member]
Loans Pledged with Federal Reserve Bank	$ 773,000,000	$ 7,500,000