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Allowance for Credit Losses and Credit Quality of Loans, Allowance for Credit Losses on Off-Balance Sheet Credit Exposures (Details) - USD ($) $ in Thousands | 9 Months Ended |  |  |  |  |
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Sep. 30, 2023 | Jun. 30, 2023 | Dec. 31, 2022 | Sep. 30, 2022 | Jun. 30, 2022 | Dec. 31, 2021
Allowance for Credit Losses and Credit Quality of Loans [Abstract] |  |  |  |  |  |
Allowance for credit losses | $ 114,601 | $ 100,400 | $ 100,800 | $ 96,800 | $ 93,600 | $ 92,000
Unfunded Commitment [Member] |  |  |  |  |  |
Allowance for Credit Losses and Credit Quality of Loans [Abstract] |  |  |  |  |  |
Allowance for credit losses | 4,800 |  | $ 5,100 |  |  |
Acquisition-related provision for credit losses | $ 800 |  |  |  |  |

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