Note 4 - Loans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Servicing Asset, Total	$ 263,400
Impaired Financing Receivable, Recorded Investment, Total	75,859	$ 106,886
Impaired Financing Receivable, Average Recorded Investment, Total	102,583	122,596	$ 127,067
Impaired Financing Receivable, Interest Income, Accrual Method, Total	$ 2,084	$ 3,166	3,302
Percentage Of Charge Off To Contractual Balances For Impaired Loans	2.10%	9.30%
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	$ 2,190	$ 1,518	1,556
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	0
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	$ 0
Minimum [Member]
Period Loan Is In Payment Default	60 days
Maximum [Member]
Period Loan Is In Payment Default	90 days
Nonaccrual Loans [Member]
Impaired Financing Receivable, Recorded Investment, Total	$ 40,500	41,800
Accruing Troubled Debt Restructuring [Member]
Impaired Financing Receivable, Recorded Investment, Total	35,400	65,100
Financing Receivable, Troubled Debt Restructuring	35,300	65,100
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	822	1,500
Non-accruing Troubled Debt Restructuring [Member]
Financing Receivable, Troubled Debt Restructuring	18,000	24,200
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	2,200	826
Residential Portfolio Segment [Member]
Servicing Asset, Total	128,400
Repossessed Assets, Total	1,000	862
Commercial Real Estate Portfolio Segment [Member]
Servicing Asset, Total	54,700
Impaired Financing Receivable, Average Recorded Investment, Total	47,612	57,596	58,635
Impaired Financing Receivable, Interest Income, Accrual Method, Total	1,366	2,125	1,618
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve		111	1,496
Commercial Construction Loans [Member]
Servicing Asset, Total	68,700
Commercial Portfolio Segment [Member]
Servicing Asset, Total	11,600
Impaired Financing Receivable, Average Recorded Investment, Total	37,475	44,486	26,957
Impaired Financing Receivable, Interest Income, Accrual Method, Total	412	685	1,303
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	2,190	1,384	$ 7
Real Estate Loan [Member]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	10,600,000	9,700,000
Commercial Loans [Member]
Loans Pledged with Federal Reserve Bank	$ 31,900	$ 21,200

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Carrying amount as of the balance sheet date of all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance; includes real and personal property; equity interests in corporations, partnerships, and joint ventures; and beneficial interests in trusts.

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