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Allowance for Credit Losses and Credit Quality of Loans, Summary (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2024 | Mar. 31, 2024 | Dec. 31, 2023 | Mar. 31, 2023 | Dec. 31, 2022
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses | $ 115,300 | $ 115,300 | $ 114,400 |  |
Percentage of allowance of credit losses | 1.19% | 1.19% | 1.19% |  |
Salisbury Bank [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Loans purchased with credit deterioration | $ 0 |  | $ 219,500 |  |
Allowance for credit losses on loans purchased |  |  | 5,800 |  |
Allowance for credit losses at acquisition |  | $ 14,500 |  |  |
Salisbury Bank [Member] | PCD [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses at acquisition |  | 5,800 |  |  |
Salisbury Bank [Member] | Non-PCD [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses at acquisition |  | 8,800 |  |  |
ASU 2022-02 [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses |  |  |  | $ 100,250 | $ 100,152
Loans [Member] | Cumulative Effect, Period of Adoption, Adjustment [Member] | ASU 2022-02 [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses |  |  |  |  | (600)
Accrued Interest Receivable [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses | 0 | 0 | 0 |  |
AIR on loans | $ 34,400 | $ 34,400 | $ 34,100 |  |
Financing Receivable, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration] | Other Assets | Other Assets | Other Assets |  |
Residential [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses | $ 23,409 | $ 23,409 | $ 22,070 |  |
Amount of loans purchased | $ 400 |  | $ 3,800 |  |
Premium on loans purchased | 7.00% |  | 7.00% |  |
Allowance for credit losses on loans purchased | $ 4 |  | $ 31 |  |
Residential [Member] | ASU 2022-02 [Member] |  |  |  |  |
Allowance for Credit Losses [Abstract] |  |  |  |  |
Allowance for credit losses |  |  |  | $ 15,390 | $ 14,539

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- Definition Amount of loans purchased with credit deterioration during the period. + References No definition available. + Details
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- Definition Percentage of allowance for credit loss to total financing receivable outstanding. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph (a) -Subparagraph (1) -Publisher SEC + Details
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- Definition Amount, after allowance for credit loss, of accrued interest on financing receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 5 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-5 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3A -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3A + Details
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