Note 3 - Loans and Allowance for Loan Losses (Details Textual) - USD ($)	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Loans and Leases Receivable, Net of Deferred Income, Total	$ 2,551,204,000		$ 2,558,552,000
Loans and Leases Receivable Period Increase (Decrease)	$ (7,300,000)
Loans and Leases Receivable, Percentage Period Increase (Decrease)	0.30%
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Outstanding Balance, Total	$ 9,200,000		11,900,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	5,000,000		$ 5,200,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	300,000	$ 200,000
Loans and Leases Receivable Nonaccrual Loans Interest Income Recognized	0	0
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	$ 100,000	$ 100,000
Minimum Number of Days Past Due at Period End For Loans Modified as Troubled Debt Restructurings	30 days

Amount of interest that was recorded on nonaccrual loans that were paid off during the period.

No definition available.

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- Definition

The percentage of increase or (decrease) during the period in loans and leases receivable during the period.

+ References

No definition available.

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- Definition

The monetary increase or (decrease) in loans and leases receivable during the period.

+ References

No definition available.

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- Definition

Represents the minimum number of days past due at period end for loans modified as troubled debt restructurings.

+ References

No definition available.

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- Definition

The recorded balance, net of any applicable reductions (for example, unamortized accretable yield and allowance for loan losses). This relates to loans not accounted for debt securities with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82894507&loc=d3e13503-111538

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- Definition

The undiscounted sum of all amounts, including amounts deemed principal, interest, fees, penalties, and other under the loan, owed to the investor at the reporting date, whether or not currently due and whether or not any such amounts have been written or charged off by the investor. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that were acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544

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- Definition

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.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 15
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-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5212-111524

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- Definition

Reflects the amount of additional interest income that would have been recorded if impaired or nonperforming loans were instead current, in compliance with their original terms, and outstanding throughout the reporting period or since origination (if held for part of the period).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 1
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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
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