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Basis of Presentation and Summary of Significant Accounting Policies (Narrative) (Details) $ in Thousands |  | 4 Months Ended | 9 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Mar. 27, 2020 USD ($) | Jul. 09, 2020 USD ($) | Sep. 30, 2021 USD ($) DerivativeInstrument | Dec. 31, 2020 USD ($) Customer | Dec. 27, 2020 USD ($) | Dec. 31, 2015 USD ($)
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Loans |  |  | $ 3,608,455 | $ 3,542,718 |  |
Offering unsecured personal loans, percentage |  | 2.95% |  |  |  |
Subordinated Notes [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Number of designated derivative instrument | DerivativeInstrument |  |  | 1 |  |  |
Debt instrument issued amount |  |  |  |  |  | $ 40,000
Subordinated Notes [Member] | LIBOR [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Debt instrument, fixed rate of interest |  |  |  |  |  | 6.00%
Debt instrument, interest rate terms |  |  | three-month LIBOR plus 3.944% |  |  |
Debt instrument, basis spread on variable rate |  |  | 3.944% |  |  |
Commercial Loan and Mortgage Loans [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Percentage of loans with active payment deferrals |  |  | 2.00% |  |  |
Residential Real Estate Loans and Lines [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Percentage of loans with active payment deferrals |  |  | 1.00% |  |  |
Maximum [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Certificate of deposit penalty fees for withdrawals |  | $ 20,000 |  |  |  |
Offering unsecured personal loans, amount |  | $ 5,000 |  |  |  |
Offering unsecured personal loans, period |  | 60 months |  |  |  |
Maximum [Member] | Consumer Indirect [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Percentage of loans with active payment deferrals |  |  | 1.00% |  |  |
CARES Act [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Estimated amount of relief fund | $ 2,200,000,000 |  |  |  |  |
Paycheck Protection Program [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Loans |  |  | $ 121,400 | 253,100 | $ 284,000,000 |
Loans forgiveness amount |  |  | 239,000 |  |  |
Paycheck Protection Program [Member] | Minimum [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Loans |  |  |  | $ 270,000 |  |
Number of customers | Customer |  |  |  | 1,700 |  |
New Paycheck Protection Program [Member] |  |  |  |  |  |
Significant Accounting Policies [Line Items] |  |  |  |  |  |
Loans |  |  | $ 107,000 |  |  |

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