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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Goodwill and Intangible Assets (Details) $ in Thousands | 1 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Nov. 30, 2013 branch | Dec. 31, 2021 | May 31, 2007 USD ($)
Partners Trust Bank | Trust Business |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Finite-lived intangible assets | $ |  |  | $ 15
Useful life (years) |  | 10 years |
Bank of America |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |
Number of branches acquired | branch | 6 |  |

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