Note 4 - Loans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Servicing Asset, Total	$ 173,500
Impaired Financing Receivable, Recorded Investment, Total	95,405	$ 75,859
Impaired Financing Receivable, Average Recorded Investment, Total	91,353	102,583	$ 122,596
Impaired Financing Receivable, Interest Income, Accrual Method, Total	$ 2,394	$ 2,084	3,166
Percentage Of Charge Off To Contractual Balances For Impaired Loans	7.10%	2.10%
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	$ 0	$ 2,190	1,518
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	0
Financing Receivable, Troubled Debt Restructuring, Commitment to Lend	0
Loans and Leases Receivable, Gross, Total	15,644,396	15,075,481
Loans and Leases Receivable, Allowance, Ending Balance	$ 166,538	123,224
SBA's Paycheck Protection Program [Member]
Financing Receivable, Number of Contracts	1,362
Loans and Leases Receivable, Gross, Total	$ 240,900
Loans and Leases Receivable, Forgiven	23,300
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	$ 67,700	40,500
Accruing Troubled Debt Restructuring [Member]
Impaired Financing Receivable, Recorded Investment, Total	27,700	35,400
Financing Receivable, Troubled Debt Restructuring	27,700	35,300
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	122	822
Non-accruing Troubled Debt Restructuring [Member]
Financing Receivable, Troubled Debt Restructuring	9,000	18,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	24	2,200
Residential Portfolio Segment [Member]
Servicing Asset, Total	110,500
Repossessed Assets, Total	808	1,000
Loans and Leases Receivable, Gross, Total	$ 4,145,389	4,088,586
Financing Receivable with Modifications, Percentage of Total Commercial Real Estate Loans	1.00%
Financing Receivable, Number of Contracts with Approved Forbearance Requests	78
Loans and Leases Receivable with Approved Forbearance Requests, Gross	$ 40,700
Commercial Real Estate Portfolio Segment [Member]
Servicing Asset, Total	30,900
Impaired Financing Receivable, Average Recorded Investment, Total	41,649	47,612	57,596
Impaired Financing Receivable, Interest Income, Accrual Method, Total	1,602	1,366	2,125
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve			111
Loans and Leases Receivable, Gross, Total	7,555,027	7,275,262
Loans and Leases Receivable, Allowance, Ending Balance	$ 49,205	33,602
Financing Receivable, Number of Contracts with Modifications	23
Loans and Leases Receivable with Modifications, Gross	$ 81,000
Financing Receivable with Modifications, Percentage of Total Commercial Real Estate Loans	1.10%
Commercial Construction Loans [Member]
Servicing Asset, Total	$ 29,000
Commercial Portfolio Segment [Member]
Servicing Asset, Total	3,100
Impaired Financing Receivable, Average Recorded Investment, Total	31,009	37,475	44,486
Impaired Financing Receivable, Interest Income, Accrual Method, Total	246	412	685
Financing Receivables, Impaired, Troubled Debt Restructuring, Specific Reserve	0	2,190	$ 1,384
Loans and Leases Receivable, Gross, Total	2,836,833	2,778,744
Loans and Leases Receivable, Allowance, Ending Balance	$ 68,742	57,021
Financing Receivable, Number of Contracts with Modifications	12
Loans and Leases Receivable with Modifications, Gross	$ 56,700
Financing Receivable with Modifications, Percentage of Total Commercial Real Estate Loans	2.00%
HELOC Loans [Member]
Financing Receivable with Modifications, Percentage of Total Commercial Real Estate Loans	0.50%
Financing Receivable, Number of Contracts with Approved Forbearance Requests	7
Loans and Leases Receivable with Approved Forbearance Requests, Gross	$ 2,200
Real Estate Loan [Member]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged	11,200,000	10,600,000
Commercial Loans [Member]
Loans Pledged with Federal Reserve Bank	$ 7,500	$ 31,900

The number of financing receivables contracts.

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The number of financing receivable contracts with approved forbearance requests.

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The number of financing receivables contracts with modifications.

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The percentage of financing receivable with modifications to total commercial real estate loans.

+ References

No definition available.

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- Definition

Reflects the amount of the specific reserve related to a troubled debt restructuring.

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- Definition

With regard to loans and leases receivable, this element represents the amount that has been forgiven.

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Amount before allowance of loans and leases held in portfolio with approved forbearance requests, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

No definition available.

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Amount before allowance of loans and leases held in portfolio with modifications, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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- Definition

Amount of the collateral pledged in support of loans with Federal Reserve Bank's Discount Window.

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No definition available.

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- Definition

Percentage of charge-off to contractual balances for impaired loans.

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Period Loan Is In Payment Default

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- Definition

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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Amount of financing receivable modified as troubled debt restructuring.

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Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default.

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- Definition

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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- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of unfunded portion of contractual agreement to lend funds to borrower for financing receivable modified as troubled debt restructuring.

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Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

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