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Note 5 - Allowance for Loan Losses, Nonperforming Assets and Impaired Loans - Impaired Loans, Average Investment and Interest Income (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Average recorded investment in impaired loans | [2] | $ 13,344 | [1] | $ 11,585 | [1] | $ 17,297
Income recognized on impaired loans, after designation as impaired |  | 528 |  | 553 |  | 769
Real Estate Construction Portfolio Segment[Member] | Construction, Other [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 3,298 |  |  |  |
Income recognized on impaired loans, after designation as impaired | [3] | 177 |  |  |  |
Real Estate Construction Portfolio Segment[Member] | Construction, 1-4 Family Residential [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] |  |  | 462 |  | 612
Income recognized on impaired loans, after designation as impaired | [3] |  |  | 10 |  | 23
Consumer Real Estate Portfolio Segment [Member] | Closed End First Liens [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 781 |  | 642 |  | 681
Income recognized on impaired loans, after designation as impaired | [3] | 57 |  | 38 |  | 43
Consumer Real Estate Portfolio Segment [Member] | Closed End Junior Liens [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 185 |  | 207 |  | 228
Income recognized on impaired loans, after designation as impaired | [3] | 11 |  | 13 |  | 15
Consumer Real Estate Portfolio Segment [Member] | Investor Owned Residential Real Estate [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 329 |  | 74 |  | 76
Income recognized on impaired loans, after designation as impaired | [3] | 1 |  | 4 |  | 5
Commercial Real Estate Portfolio Segment [Member] | Multifamily Real Estate [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 748 |  | 1,366 |  | 2,581
Income recognized on impaired loans, after designation as impaired | [3] | 16 |  | 12 |  | 84
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate, Owner Occupied [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 4,047 |  | 4,342 |  | 6,141
Income recognized on impaired loans, after designation as impaired | [3] | 200 |  | 206 |  | 251
Commercial Real Estate Portfolio Segment [Member] | Commercial Real Estate Other [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 2,638 |  | 3,947 |  | 5,888
Income recognized on impaired loans, after designation as impaired | [3] |  |  | 263 |  | 308
Commercial Non Real Estate Segment [Member] | Commercial and Industrial [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 1,282 |  | 541 |  | 1,090
Income recognized on impaired loans, after designation as impaired | [3] | 64 |  | 7 |  | $ 40
Consumer Non Real Estate Portfolio Segment [Member] | Automobile Loan [Member] |  |  |  |  |  |
Average recorded investment in impaired loans | [2],[3] | 36 |  | 4 |  |
Income recognized on impaired loans, after designation as impaired | [3] | $ 2 |  | $ 0 |  |
[1] | Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.
[2] | Recorded investment is net of charge-offs and interest paid while a loan is in nonaccrual status.
[3] | Only classes with impaired loans are shown.

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