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LOANS AND ALLOWANCE FOR LOAN LOSSES - Troubled Debt Restructuring Narrative (Details) | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2020 USD ($) contract loan borrower | Sep. 30, 2019 USD ($) contract | Sep. 30, 2020 USD ($) loan contract | Sep. 30, 2019 USD ($) contract loan | Dec. 31, 2019 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 3 |  | 15 | 2 |
Financing Receivable, Troubled Debt Restructuring, Postmodification | $ | $ 1,458,000 |  | $ 5,100,000 | $ 4,360,000 |
Financing Receivable, Troubled Debt Restructuring | $ | 10,800,000 |  | 10,800,000 |  | $ 9,000,000.0
Financing Receivable, Troubled Debt Restructuring, Purchased with Credit Deterioration, Increase | $ | 600,000 |  | 600,000 |  | 2,300,000
Financing Receivable, Modifications, Recorded Investment, Still Accruing | $ | 2,800,000 |  | 2,800,000 |  | 900,000
Financing Receivable, Modifications, Recorded Investment, Nonaccrual Status | $ | 8,000,000.0 |  | 8,000,000.0 |  | 8,100,000
Additional Amounts Committed to Customers with Loans Classified as Troubled Debt Restructurings | $ | 37,000 |  | 37,000 |  | $ 17,000
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down | $ | $ 0 | $ 0 | $ 0 | $ 0 |
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts | contract | 0 | 0 | 0 | 0 |
Allowance for Loan and Lease Losses, Period Increase (Decrease) | $ |  |  | $ 142,000 | $ 1,700,000 |
Interest Rate Below Market Reduction |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Modifications, Number of Days Past Due | 30 days |  |  |  |
Interest Rate Below Market Reduction | Commercial and industrial |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 2 |  |  |  |
Interest Rate Below Market Reduction | Commercial and industrial | Non-accrual Status |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 1 |  |  |  |
Principal Forgiveness |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Financing Receivable, Modifications, Extension Period |  |  |  | 3 years |
Commercial mortgages | Interest Rate Below Market Reduction |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 4 |  |  |  |
Financing Receivable, Modifications, Number of Borrowers | borrower | 3 |  |  |  |
Commercial mortgages | Interest Rate Below Market Reduction | Substandard | Non-accrual Status |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 3 |  |  |  |
Commercial mortgages | Interest Rate Below Market Reduction | Substandard | Non-accrual Status | 30 - 59 Days Past Due |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 2 |  |  |  |
Home equity lines and loans | Interest Rate Below Market Reduction |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 3 |  |  |  |
Home equity lines and loans | Interest Rate Below Market Reduction | Substandard | Non-accrual Status |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 3 |  |  |  |
Residential mortgages | Interest Rate Below Market Reduction |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 3 |  |  |  |
Residential mortgages | Interest Rate Below Market Reduction | Non-accrual Status |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 3 |  |  |  |
Residential mortgages | Interest Rate Below Market Reduction | Substandard | Non-accrual Status |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 2 |  |  |  |
Residential mortgages | Interest Rate Below Market Reduction | Substandard | Non-accrual Status | 30 - 59 Days Past Due |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 1 |  |  |  |
Commercial And Consumer Portfolio Segment |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans |  |  | 1,125 |  |
Financing Receivable, Troubled Debt Restructuring, Postmodification | $ |  |  | $ 233,600,000 |  |
Number of Loans Remaining in Modified Status | 74 |  | 74 |  |
Loan Balance Remaining in Modified Status | $ | $ 45,900,000 |  | $ 45,900,000 |  |
Number of Loans Remaining in Modified Status, Modified More than Once | 44 |  | 44 |  |
Loan Balance Remaining in Modified Status, Modified More than Once | $ | $ 32,800,000 |  | $ 32,800,000 |  |
Consumer loans: | Home equity lines and loans |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans | 0 |  | 3 | 1 |
Financing Receivable, Troubled Debt Restructuring, Postmodification | $ | $ 0 |  | $ 738,000 | $ 137,000 |
Consumer loans: | Home equity lines and loans | Interest Rate Below Market Reduction |  |  |  |  |
Financing Receivable, Troubled Debt Restructuring [Line Items] |  |  |  |  |
Number of loans |  |  |  | 1 |

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