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Fair Market Value of Financial Assets and Liabilities (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016 | Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | $ 603,033 | $ 605,394 |  | $ 603,033 |  | $ 605,394
Reconciliation of beginning and ending balances of recurring fair value measurements recognized in balance sheet using significant unobservable (Level 3) inputs [Roll Forward] |  |  |  |  |  |
Total losses | (119) |  | $ 0 | $ (419) | $ (660) |
Minimum [Member] |  |  |  |  |  |
Other real estate owned [Abstract] |  |  |  |  |  |
Typical frequency of periodic reviews |  |  |  | 12 months |  |
Maximum [Member] |  |  |  |  |  |
Other real estate owned [Abstract] |  |  |  |  |  |
Typical frequency of periodic reviews |  |  |  | 18 months |  |
Frequency of periodic reviews in general |  |  |  | 24 months |  |
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 89,613 | 69,292 |  | $ 89,613 |  | 69,292
Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 513,420 | 536,102 |  | 513,420 |  | 536,102
Significant Unobservable Inputs (Level 3) [Member] | Fair Value [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Fair Value [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Mortgage servicing rights | 3,283 | 3,433 |  | 3,283 |  | 3,433
Recurring [Member] | Fair Value [Member] | U.S. Treasury and Government Agencies [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 217,858 | 222,464 |  | 217,858 |  | 222,464
Recurring [Member] | Fair Value [Member] | State and Political Subdivisions [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 136,657 | 133,516 |  | 136,657 |  | 133,516
Recurring [Member] | Fair Value [Member] | U.S. Government Sponsored Agency Mortgage-backed Securities [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 223,998 | 225,056 |  | 223,998 |  | 225,056
Recurring [Member] | Fair Value [Member] | CRA Investments Funds [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 24,520 | 24,358 |  | 24,520 |  | 24,358
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Mortgage servicing rights | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member] | U.S. Treasury and Government Agencies [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 65,093 | 44,934 |  | 65,093 |  | 44,934
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member] | State and Political Subdivisions [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member] | U.S. Government Sponsored Agency Mortgage-backed Securities [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member] | CRA Investments Funds [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 24,520 | 24,358 |  | 24,520 |  | 24,358
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Mortgage servicing rights | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | U.S. Treasury and Government Agencies [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 152,765 | 177,530 |  | 152,765 |  | 177,530
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | State and Political Subdivisions [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 136,657 | 133,516 |  | 136,657 |  | 133,516
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | U.S. Government Sponsored Agency Mortgage-backed Securities [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 223,998 | 225,056 |  | 223,998 |  | 225,056
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] | CRA Investments Funds [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Mortgage servicing rights | 3,283 | 3,433 |  | 3,283 |  | 3,433
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value [Member] | U.S. Treasury and Government Agencies [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value [Member] | State and Political Subdivisions [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value [Member] | U.S. Government Sponsored Agency Mortgage-backed Securities [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value [Member] | CRA Investments Funds [Member] |  |  |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |
Available-for-sale securities | 0 | 0 |  | 0 |  | 0
Recurring [Member] | Mortgage Servicing Rights [Member] |  |  |  |  |  |
Reconciliation of beginning and ending balances of recurring fair value measurements recognized in balance sheet using significant unobservable (Level 3) inputs [Roll Forward] |  |  |  |  |  |
Beginning balance | 3,304 | 2,964 | 2,797 | 3,433 | 3,236 | 3,236
Total recognized gains (losses) Included in net income | 5 |  | 118 | (73) | (422) |
Issues | 98 |  | 167 | 269 | 388 |
Settlements | (124) |  | (118) | (346) | (238) |
Ending balance | 3,283 | 3,433 | 2,964 | 3,283 | 2,964 | 3,433
Total gains (losses) for the period included in net income attributable to the change in unrealized gains or losses related to assets still held at the reporting date | 5 |  | 118 | (73) | (422) |
Nonrecurring [Member] |  |  |  |  |  |
Impaired loan (collateral dependent) [Abstract] |  |  |  |  |  |
Impaired loans, fair value adjustments | 300 | 300 | 300 | 700 | 600 | 600
Other real estate owned [Abstract] |  |  |  |  |  |
Other real estate /assets owned, fair value adjustment | 900 | 600 | $ 400 | 2,900 | $ 600 | 1,200
Nonrecurring [Member] | Fair Value [Member] |  |  |  |  |  |
Assets measured-nonrecurring basis [Abstract] |  |  |  |  |  |
Impaired loans (collateral dependent) | 1,732 | 5,506 |  | 1,732 |  | 5,506
Other real estate /assets owned | 18,843 | 4,388 |  | 18,843 |  | 4,388
Nonrecurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Fair Value [Member] |  |  |  |  |  |
Assets measured-nonrecurring basis [Abstract] |  |  |  |  |  |
Impaired loans (collateral dependent) | 0 | 0 |  | 0 |  | 0
Other real estate /assets owned | 0 | 0 |  | 0 |  | 0
Nonrecurring [Member] | Significant Other Observable Inputs (Level 2) [Member] | Fair Value [Member] |  |  |  |  |  |
Assets measured-nonrecurring basis [Abstract] |  |  |  |  |  |
Impaired loans (collateral dependent) | 0 | 0 |  | 0 |  | 0
Other real estate /assets owned | 0 | 0 |  | 0 |  | 0
Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member] | Fair Value [Member] |  |  |  |  |  |
Assets measured-nonrecurring basis [Abstract] |  |  |  |  |  |
Impaired loans (collateral dependent) | 1,732 | 5,506 |  | 1,732 |  | 5,506
Other real estate /assets owned | $ 18,843 | $ 4,388 |  | $ 18,843 |  | $ 4,388

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