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Loans and Allowance for Loan Losses - Troubled Debt Restructurings (Details) | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2020 USD ($) loan | Mar. 31, 2019 loan | Dec. 31, 2020 USD ($) loan | Dec. 31, 2019 USD ($)
Troubled debt restructuring |  |  |  |
Number of loan modifications not considered TDRs, in connection with CARES Act | 577 |  | 577 |
Loan modifications not considered TDRS, in connection with CARES Act | $ 153,600,000 |  | $ 153,600,000 |
Maximum |  |  |  |
Troubled debt restructuring |  |  |  |
Typical loan deferral period under the CARES Act |  |  | 90 days |
Extending amortization period |  |  |  |
Troubled debt restructuring |  |  |  |
Number of loans modified as a troubled debt restructuring | loan |  | 1 |  |
Carrying value of restructured loan |  |  |  | $ 200,000
Specific reserve for loan losses allocated |  |  |  | $ 24,000
Interest Rate Below Market Reduction |  |  |  |
Troubled debt restructuring |  |  |  |
Number of loans modified as a troubled debt restructuring | loan | 1 |  |  |
Carrying value of restructured loan |  |  | $ 2,600,000 |
Specific reserve for loan losses allocated | $ 0 |  | $ 0 |
Second Deferral |  |  |  |
Troubled debt restructuring |  |  |  |
Number of loan modifications not considered TDRs, in connection with CARES Act | loan | 18 |  | 18 |
Loan modifications not considered TDRS, in connection with CARES Act | $ 8,400,000 |  | $ 8,400,000 |
First Deferral |  |  |  |
Troubled debt restructuring |  |  |  |
Number of loan modifications not considered TDRs, in connection with CARES Act | loan | 21 |  | 21 |
Loan modifications not considered TDRS, in connection with CARES Act | $ 3,700,000 |  | $ 3,700,000 |

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