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v3.21.1

Loans (Narrative) (Details) | 3 Months Ended | 12 Months Ended | 15 Months Ended |
--- | --- | --- | --- | ---
Mar. 31, 2021 USD ($) contract | Mar. 31, 2020 contract | Dec. 31, 2020 USD ($) | Mar. 31, 2021 USD ($) | Dec. 27, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans held for sale | $ 5,685,000 |  | $ 4,305,000 | $ 5,685,000 |
Loans | 3,604,558,000 |  | 3,542,718,000 | 3,604,558,000 |
Past due greater than 90 days and still accruing interest | 0 |  | 0 | $ 0 |
Interest income on nonaccrual loans | $ 0 |  | 0 |  |
Number of loans modified as TDR | contract | 0 | 0 |  |  |
Number of loans modified as TDR that defaulted within the previous 12 months | contract | 0 | 0 |  |  |
Days past due when loans are generally placed on nonaccrual status, in days | 90 days | 90 days |  |  |
ASU 2016-13 [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Change in Accounting Principle, Accounting Standards Update, Adopted | true |  |  | true |
Change in Accounting Principle, Accounting Standards Update, Adoption Date | Jan. 01, 2020 |  |  | Jan. 01, 2020 |
Change in retained earnings |  |  |  | $ 8,700,000 |
Increase (decrease) in deferred tax assets |  |  |  | 3,000,000.0 |
ASU 2016-13 [Member] | Held To Maturity Investment Securities [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Increase in the allowance for credit losses on loans |  |  |  | 14,000 |
Other Assets [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Accrued interest receivable | $ 13,700,000 |  | 13,600,000 | 13,700,000 |
Deferral [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans | 89,100,000 |  | 113,000,000.0 | 89,100,000 |
Paycheck Protection Program [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans | 262,100,000 |  | 253,100,000 | 262,100,000 | $ 284,000,000,000
COVID-19 [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans |  |  | 532,400,000 |  |
Residential Real Estate Loans [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Loans held for sale | 5,700,000 |  | 4,300,000 | 5,700,000 |
Consumer Overdrafts [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Past due greater than 90 days and still accruing interest | $ 284,000 |  | $ 231,000 | 284,000 |
Loans [Member] | ASU 2016-13 [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Increase in the allowance for credit losses on loans |  |  |  | 9,600,000 |
Unfunded Commitments [Member] | ASU 2016-13 [Member] |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |
Increase in the allowance for credit losses on loans |  |  |  | $ 2,100,000 |

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