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v3.19.1

Investment Securities - Additional Information (Details) $ in Thousands | 3 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Mar. 31, 2019 USD ($) security state | Mar. 31, 2018 USD ($) security | Dec. 31, 2018 USD ($) security | Sep. 30, 2014 USD ($)
Investment [Line Items] |  |  |  |
Number of securities temporarily impaired (security) | security | 291 | 457 | 511 |
Number of securities temporarily impaired for twelve months or more (security) | security | 274 | 159 | 232 |
Length of time securities temporarily impaired (months) | 12 months | 12 months | 12 months |
Amortized cost of transferred securities from available-for-sale to held-to-maturity |  |  |  | $ 89,780
Fair value of transferred securities from available-for-sale to held-to-maturity |  |  |  | 89,757
Net unrealized loss, net of taxes on transferred securities |  |  |  | $ 15
Unamortized balance of net unrealized losses | $ 194 | $ 182 | $ 197 |
Number of states in New England where FHLB serve (state) | state | 6 |  |  |
Federal Home Loan Bank Stock | $ 7,945 | 10,910 | 10,549 |
Other equity securities |  |  |  |
Investment [Line Items] |  |  |  |
Fair value of securities pledged as collateral | $ 189,711 | $ 197,349 | $ 222,829 |
State and political subdivisions |  |  |  |
Investment [Line Items] |  |  |  |
Percentage of overall security holdings downgraded | 0.40% |  |  |

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