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LOANS AND ALLOWANCE FOR CREDIT LOSSES - Narrative (Details) | 3 Months Ended | 9 Months Ended | 12 Months Ended
--- | --- | --- | ---
Sep. 30, 2021 USD ($) | Jun. 30, 2021 USD ($) | Mar. 31, 2021 USD ($) | Sep. 30, 2020 USD ($) | Sep. 30, 2021 USD ($) Contract | Sep. 30, 2020 USD ($) | Dec. 31, 2020 USD ($) Contract
Financing Receivable Allowance For Credit Losses [Line Items] |  |  |  |  |  |  |
Allowance for credit losses provision | $ (700,000) |  |  | $ (300,000) | $ (1,700,000) | $ 13,200,000 |
Loans classified in doubtful or loss risk rating | 0 |  |  |  | $ 0 |  | $ 0
Number of loans modified as TDRs | Contract |  |  |  |  | 1 |  | 4
Increase in allowance for loan losses due to TDRs |  |  |  |  | $ 0 |  | $ 0
Troubled debt restructuring charge-offs |  |  |  |  | $ 0 |  | 0
COVID-19 |  |  |  |  |  |  |
Financing Receivable Allowance For Credit Losses [Line Items] |  |  |  |  |  |  |
Allowance for credit losses provision |  |  |  |  |  |  | $ 13,200,000
Provision for Other Credit Losses | $ 700,000 | $ 1,000,000 | $ 0 |  |  |  |

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