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Note 4 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Loans Past Due 90 Days or More and Impaired Loans (Details) - USD ($) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2016 | Sep. 30, 2015 | Dec. 31, 2015
Loans past due 90 days or more and still accruing |  | $ 195,000 | [1] | $ 47,000 |  | $ 156,000 |
Ratio of loans past due 90 days or more and still accruing to loans, net of unearned income and deferred fees |  | 0.03% |  | 0.01% |  | 0.03% |
Accruing restructured loans |  | $ 4,662,000 |  | $ 6,080,000 |  | $ 8,814,000 |
Impaired loans: |  |  |  |  |  |  |
Impaired loans with no valuation allowance |  | 9,290,000 | [2] | 12,548,000 |  | 12,973,000 | [2]
Impaired loans with a valuation allowance |  | 620,000 | [2] | 2,464,000 |  | 2,373,000 | [2]
Total impaired loans |  | 9,910,000 | [2] | 15,012,000 |  | 15,346,000 | [2]
Valuation allowance |  | (27,000) |  | (144,000) |  | (45,000) |
Impaired loans, net of allowance |  | 9,883,000 |  | 14,868,000 |  | 15,301,000 |
Average recorded investment in impaired loans(1) | [3],[4] | 12,908,000 |  | 15,902,000 | [5] | 17,297,000 |
Interest income recognized on impaired loans, after designation as impaired |  | 476,000 |  | 267,000 | [5] | 769,000 |
Amount of income recognized on a cash basis |  | $ 0 |  | $ 0 |  | $ 0 |
[1] | Only classes with past-due or nonaccrual loans are shown.
[2] | Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.
[3] | Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.
[4] | Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.
[5] | Only classes with impaired loans are shown.

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- Definition Represents ratio of loans past due 90 days or more and still accruing to loans, net of unearned income and deferred fees. + References No definition available. + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5212-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5258-111524 + Details
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