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Loans and Allowance for Loan Losses - Troubled Debt Restructuring by Class (Details) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2018 loan | Dec. 31, 2018 USD ($) loan | Dec. 31, 2017 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Number of loans removed from TDR resignation | loan |  |  | 0
Recorded investment of loans removed from TDR resignation |  | $ 247,000 |
Recorded investment in Troubled Debt Restructurings |  | 14,406,000 | $ 16,520,000
Acquired loans included in TDR |  | $ 0 | 0
TDR loans on non-accrual status | loan |  | 2 |
TDR loans on non-accrual status, value |  | $ 65,000 |
TDR loans accruing interest as of period end |  |  | 0
Commercial | Commercial and industrial |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Recorded investment in Troubled Debt Restructurings |  | 1,506,000 | 2,165,000
Commercial real estate | Commercial real estate, owner-occupied |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Recorded investment in Troubled Debt Restructurings |  | 6,993,000 | 6,999,000
Commercial real estate | Commercial real estate, investor |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Recorded investment in Troubled Debt Restructurings |  | 1,821,000 | 2,171,000
Commercial real estate | Construction |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Recorded investment in Troubled Debt Restructurings |  | 2,688,000 | 2,969,000
Residential loans | Home equity |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Number of loans removed from TDR resignation | loan | 1 |  |
Recorded investment in Troubled Debt Restructurings |  | $ 251,000 | 347,000
Residential loans | Other residential |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Number of loans removed from TDR resignation | loan |  | 1 |
Recorded investment in Troubled Debt Restructurings |  | $ 462,000 | 1,148,000
Consumer loans | Installment and other consumer |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Recorded investment in Troubled Debt Restructurings |  | $ 685,000 | $ 721,000

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