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v3.19.3.a.u2

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2019 USD ($) Calculation Type Subsidiary County Branch Factor Component Trust Segment | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | Subsidiary | 2 |  |
Number of unconsolidated subsidiary business trusts owned | Trust | 1 |  |
Number of bank branches | Branch | 231 |  |
Risks and Uncertainties [Abstract] |  |  |
Number of main components of economic risk | Component | 3 |  |
Wealth Management Services [Abstract] |  |  |
Number of types of performance obligations | Type | 2 |  |
Contract Balances [Abstract] |  |  |
Accounts receivable | $ 26.8 | $ 26.4 |
Unbilled fee revenue | 7.5 | 7.8 |
Unearned revenue | 1.8 | 2.2 |
Cash and Cash Equivalents [Abstract] |  |  |
Cash due from banks | $ 10.4 | 15.0 |
Impaired and Other Nonaccrual Loans [Abstract] |  |  |
Number of days past due for loans to be placed on nonaccrual status | 90 days |  |
Period for which a nonaccrual TDR loan remains on nonaccrual status | 12 months |  |
Allowance for Loan Losses [Abstract] |  |  |
Number of broad components used in allowance methodology | Component | 2 |  |
Number of calculations used for general loan loss allocations | Calculation | 2 |  |
Number of main loan segments | Segment | 5 |  |
Period of historical net charge-off data for each loan class used in determining allowance level | 36 months |  |
Number of qualitative environmental factors used in qualitative calculation for general loan loss allocations | Factor | 8 |  |
Other Real Estate [Abstract] |  |  |
Other real estate | $ 1.3 | 1.3 |
Advertising [Abstract] |  |  |
Advertising costs | 7.1 | $ 5.1 | $ 5.7
ASU 2016-07 [Member] |  |  |
Investments in Real Estate Limited Partnerships [Abstract] |  |  |
Unfunded commitments | 0.4 |  |
Impairment losses related to real estate partnerships | $ 0.0 |  |
Investments in Real Estate Limited Partnerships [Member] | Minimum [Member] |  |  |
Investments in Real Estate Limited Partnerships [Abstract] |  |  |
Ownership interest | 5.00% |  |
Investments in Real Estate Limited Partnerships [Member] | Maximum [Member] |  |  |
Investments in Real Estate Limited Partnerships [Abstract] |  |  |
Ownership interest | 99.99% |  |
Upstate New York [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | County | 40 |  |
Northeastern Pennsylvania [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | County | 6 |  |
Vermont [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | County | 12 |  |
Western Massachusetts [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of counties where the bank has facilities | County | 1 |  |
Consumer Installment Loans [Member] |  |  |
Impaired and Other Nonaccrual Loans [Abstract] |  |  |
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property | 90 days |  |
Consumer Mortgage Loans [Member] |  |  |
Impaired and Other Nonaccrual Loans [Abstract] |  |  |
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property | 180 days |  |
Home Equity Loans [Member] |  |  |
Impaired and Other Nonaccrual Loans [Abstract] |  |  |
Number of days past due after which loans are charged off to the extent outstanding principal balance exceeds fair value of collateral/property | 180 days |  |
Equipment [Member] | Minimum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 2 years |  |
Equipment [Member] | Maximum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 20 years |  |
Software [Member] | Minimum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 3 years |  |
Software [Member] | Maximum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 7 years |  |
Hardware [Member] | Minimum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 3 years |  |
Hardware [Member] | Maximum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 7 years |  |
Building and Building Improvements [Member] | Minimum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 10 years |  |
Building and Building Improvements [Member] | Maximum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 40 years |  |
Land Improvements [Member] | Maximum [Member] |  |  |
Property, Plant and Equipment, Gross [Abstract] |  |  |
Estimated useful life | 20 years |  |
BPAS [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | Subsidiary | 5 |  |
Hand Benefits & Trust [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | Subsidiary | 1 |  |
NRS [Member] |  |  |
Nature of Operations [Abstract] |  |  |
Number of significant consolidated subsidiaries owned | Subsidiary | 1 |  |
Core Deposits [Member] | Minimum [Member] |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 7 years |  |
Core Deposits [Member] | Maximum [Member] |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 20 years |  |
Customer Relationships [Member] | Minimum [Member] |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 7 years |  |
Customer Relationships [Member] | Maximum [Member] |  |  |
Intangible Assets [Abstract] |  |  |
Intangible asset useful life (amortization period) | 20 years |  |
Commercial Portfolio Segment [Member] | Minimum [Member] |  |  |
Impaired and Other Nonaccrual Loans [Abstract] |  |  |
Threshold balance of loans individually evaluated for impairment | $ 0.5 |  |

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