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Note 4 - Loans and Related Allowance for Loan and Lease Losses - Troubled Debt Restructurings Subsequently Defaulted (Details) |  | 12 Months Ended
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Dec. 31, 2015 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($)
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  | 0 |  |
Commercial And Industrial [Member] |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  |  | 2 | 2
Recorded investment, subsequently defaulted |  |  | $ 7,000 | $ 14,000
Number of contracts, subsequently defaulted | $ 434,000 | $ 127,000 | 610,000 |
Real Estate Construction Porfolio Segment [Member] |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  |  |  | 1
Recorded investment, subsequently defaulted |  |  |  | $ 130,000
Number of contracts, subsequently defaulted | 181,000 |  | $ 1 |
Real Estate Mortgage Portfolio Segment [Member] | Residential Loan [Member] |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  |  | 4 |
Recorded investment, subsequently defaulted |  |  | $ 278,000 |
Number of contracts, subsequently defaulted | 535,000 | $ 256,000 | $ 166,000 |
Commercial Real Estate Portfolio Segment [Member] |  |  |  |
Financing Receivable, Modifications, Subsequent Default, Number of Contracts |  |  | 1 |
Recorded investment, subsequently defaulted |  |  | $ 119,000 |
Number of contracts, subsequently defaulted | $ 270,000 |  | $ 311,000 |

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- Definition Post-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524 + Details
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- Definition Number of financing receivables that have been modified by troubled debt restructurings within the previous 12 months and for which there was a payment default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524 + Details
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- Definition Amount of investment related to financing receivables modified by troubled debt restructurings within the previous 12 months, for which there was a payment default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524 + Details
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