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Derivative Instruments and Hedge Activities - Summary of Cash Flow Hedges (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016
Derivative [Line Items] |  |
Notional Amount | $ 344,726,000 | $ 151,213,000
Derivative assets fair value | 5,981,000 | 4,317,000
Derivative liabilities fair value | 994,000 | $ 559,000
Cash Flow Hedges |  |
Derivative [Line Items] |  |
Notional Amount | 250,000,000 |
Derivative assets fair value | 5,030,000 |
Derivative liabilities fair value | $ 38,000 |
Weighted average pay rates | 1.67% |
Weighted average receive rates | 1.63% |
Weighted average maturity | 4 years 2 months 12 days |

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