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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2021 USD ($) item segment component country subsidiary Office | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | subsidiary | 2 |  |
Number of bank branches | Office | 206 |  |
Number Of Operating Location | item | 12 |  |
Risks and Uncertainties [Abstract] |  |  |
Number of main components of economic risk | component | 3 |  |
Wealth Management Services [Abstract] |  |  |
Number of types of performance obligations | item | 2 |  |
Contract Balances [Abstract] |  |  |
Accounts receivable | $ 31.6 | $ 30.3 |
Unbilled fee revenue | 9.1 | 7.7 |
Unearned revenue | 2.2 | 1.4 |
Cash and Cash Equivalents [Abstract] |  |  |
Cash due from banks | 11.0 | 7.7 |
Allowance for Loan Losses [Abstract] |  |  |
Accrued interest and fees receivable | 16.7 | 22.2 |
Other Real Estate [Abstract] |  |  |
Other real estate | 0.7 | 0.9 |
Investments in Real Estate Limited Partnerships [Abstract] |  |  |
Unfunded commitments | 0.2 |  |
Impairment losses related to real estate partnerships | 0.0 |  |
Advertising [Abstract] |  |  |
Advertising costs | 5.2 | 6.1 | $ 7.1
Available-for-sale Securities [Member] |  |  |
Allowance for Loan Losses [Abstract] |  |  |
Accrued interest and fees receivable | $ 15.8 | $ 13.3 |
Land Improvements [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 20 years |  |
Minimum | LIHTC [Member] |  |  |
Investments in Real Estate Limited Partnerships [Abstract] |  |  |
Ownership interest | 5.00% |  |
Minimum | Equipment [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 2 years |  |
Minimum | Software [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 3 years |  |
Minimum | Hardware [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 3 years |  |
Minimum | Building and Building Improvements [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 10 years |  |
Minimum | Core deposit intangibles |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 7 years |  |
Minimum | Customer Relationships [Member] |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 7 years |  |
Maximum |  |  |
Impaired and Other Nonaccrual Loans [Abstract] |  |  |
Threshold balance of loans individually evaluated for impairment | $ 0.5 |  |
Maximum | LIHTC [Member] |  |  |
Investments in Real Estate Limited Partnerships [Abstract] |  |  |
Ownership interest | 99.99% |  |
Maximum | Equipment [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 20 years |  |
Maximum | Software [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 7 years |  |
Maximum | Hardware [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 7 years |  |
Maximum | Building and Building Improvements [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 40 years |  |
Maximum | Core deposit intangibles |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 20 years |  |
Maximum | Customer Relationships [Member] |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 20 years |  |
BPAS [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | segment | 5 |  |
Hand Benefits & Trust [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | segment | 1 |  |
NRS [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | segment | 1 |  |
Upstate New York. |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | country | 42 |  |
PENNSYLVANIA |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | country | 6 |  |
Vermont [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | country | 12 |  |
Massachusetts [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | country | 1 |  |

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