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Note 4 - Loans and Related Allowance for Loan and Lease Losses - Troubled Debt Restructurings (Details) |  | 12 Months Ended
--- | --- | ---
Dec. 31, 2015 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Commercial And Industrial [Member] |  |  |
Number of contracts | 6 | 4 | 5
Pre-modification outstanding recorded investment | $ 434,000 | $ 127,000 | $ 610,000
Post-modification outstanding recorded investment | $ 434,000 | $ 127,000 | $ 610,000
Real Estate Mortgage Portfolio Segment [Member] | Residential Loan [Member] |  |  |
Number of contracts | 6 | 5 | 4
Pre-modification outstanding recorded investment | $ 515,000 | $ 256,000 | $ 166,000
Post-modification outstanding recorded investment | $ 535,000 | $ 256,000 | 166,000
Real Estate Construction Porfolio Segment [Member] |  |  |
Number of contracts | 1 |  |
Pre-modification outstanding recorded investment | $ 181,000 |  |
Post-modification outstanding recorded investment | $ 181,000 |  | $ 1
Commercial Real Estate Portfolio Segment [Member] |  |  |
Number of contracts | 1 |  | 1
Pre-modification outstanding recorded investment | $ 270,000 |  | $ 311,000
Post-modification outstanding recorded investment | $ 270,000 |  | $ 311,000
Extended Maturity [Member] | Commercial And Industrial [Member] |  |  |
Number of contracts | 6 | 4 | 5
Extended Maturity [Member] | Real Estate Mortgage Portfolio Segment [Member] | Residential Loan [Member] |  |  |
Number of contracts | 5 | 5 | 4
Extended Maturity [Member] | Real Estate Construction Porfolio Segment [Member] |  |  |
Number of contracts | 1 |  |
Extended Maturity [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |
Number of contracts | 1 |  | 1
Other Restructurings [Member] | Commercial And Industrial [Member] |  |  |
Number of contracts |  |  |
Other Restructurings [Member] | Real Estate Mortgage Portfolio Segment [Member] | Residential Loan [Member] |  |  |
Number of contracts | 1 |  |
Other Restructurings [Member] | Real Estate Construction Porfolio Segment [Member] |  |  |
Number of contracts |  |  |
Other Restructurings [Member] | Commercial Real Estate Portfolio Segment [Member] |  |  |
Number of contracts |  |  |

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- Definition Number of financing receivables that have been 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 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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