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Summary of Significant Accounting Policies - Dividend (Details) - USD ($) |  | 12 Months Ended |
--- | --- | --- | ---
Jan. 16, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Jan. 15, 2019
90-Days or Greater Past Due Loans |  |  |  |  |
Period from due date after which accrual of interest income is discontinued |  | 90 days |  |  |
Accumulated other comprehensive income (loss) breakdown |  |  |  |  |
Unrealized gains on securities |  | $ 4,000,000 |  |  |
Unrealized losses on securities |  |  | $ 2,200,000 |  |
Unrealized Loss on Price Risk Cash Flow Derivatives, before Tax |  | 41,000 | 760,000 |  |
Goodwill and Core Deposit Intangible |  |  |  |  |
Impairment of goodwill |  | 0 |  |  |
Amortization of core deposit intangible |  | 387,000 | 96,000 | $ 16,000 |
Core Deposit Intangible |  |  |  |  |
Goodwill and Core Deposit Intangible |  |  |  |  |
Amortization of core deposit intangible |  | 387,000 |  |  |
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] |  |  |  |  |
Estimated future amortization expense for the core deposit intangible for the year ending December 31, 2020 |  | 483,000 |  |  |
Estimated future amortization expense for the core deposit intangible for the year ending December 31, 2021 |  | 416,000 |  |  |
Estimated future amortization expense for the core deposit intangible for the year ending December 31, 2022 |  | 380,000 |  |  |
Estimated future amortization expense for the core deposit intangible for the year ending December 31, 2023 |  | 372,000 |  |  |
Estimated future amortization expense for the core deposit intangible for the year ending December 31, 2024 |  | 372,000 |  |  |
Core Deposit Intangible | Talmer |  |  |  |  |
Goodwill and Core Deposit Intangible |  |  |  |  |
Remaining intangible asset |  | $ 465,000 |  |  |
Core Deposit Intangible | GCFC/ABC Bank |  |  |  |  |
Goodwill and Core Deposit Intangible |  |  |  |  |
Useful life (in years) |  | 10 years |  |  |
Intangible asset recorded |  | $ 3,100,000 |  |  |
Remaining intangible asset |  | 2,700,000 |  |  |
Subsequent Event |  |  |  |  |
Subsequent Events |  |  |  |  |
Dividends Payable, Amount Per Share |  |  |  |  | $ 0.01
Warrants to purchase shares of common stock | 815,339 |  |  |  |
Exercise price of warrant | $ 13.43 |  |  |  |
Market price per share | $ 14.23 |  |  |  |
Number os shares issued | 45,836 |  |  |  |
Reduction in additional paid up capital | $ 313,000 |  |  |  |
All other |  |  |  |  |
Allowance for Loan Losses |  |  |  |  |
Unallocated component of allowance |  | $ 537,000 | $ 542,000 | $ 435,000 |

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