Interest on deposits Interest Expense, Deposits Financial assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Amortized Cost, Due in 5 to 10 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Hedging Designation [Domain] Hedging Designation [Domain] Amortized cost of securities transferred Available-for-Sale Securities, Transferred Security, at Carrying Value Available-for-Sale Securities, Transferred Security, at Carrying Value Accumulated Net Investment Gain (Loss) Attributable to Parent AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member] Unamortized gain Defined Benefit Plan, Benefit Obligation, Actuarial Gain (Loss) Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy and NAV [Domain] NET INCOME      Net income Net income as reported Net Income (Loss) Attributable to Parent Right of use lease asset Operating Lease, Right-of-Use Asset Ending balance collectively evaluated for impairment Financing Receivable, Collectively Evaluated for Impairment Construction loans, percent of capital Construction Loans Actual Loan Portfolio To Company Capital The ratio of loan portfolio to Company capital for construction loans . Net unrealized loss on securities transferred from available for sale to held to maturity Unamortized balance of net unrealized losses transferred Other Comprehensive Income (Loss), Accumulated Unrealized Gain (Loss) on Transfer of Available-for-sale Securities to Held-to-maturity Other Comprehensive Income (Loss), Accumulated Unrealized Gain (Loss) on Transfer of Available-for-sale Securities to Held-to-maturity Restricted equity securities, at cost Restricted Equity Securities, At Cost Amount of stock held at Federal Home Loan Bank and Federal Reserve Bank. Federal Home Loan Bank (FHLB) stock and Federal Reserve Bank Stock represents an equity interest in a FHLB of FRB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). Interest cost Defined Benefit Plan, Interest Cost Derivative liabilities Derivative Liability Equity Securities, Restricted [Abstract] Equity Securities, Restricted [Abstract] Security Exchange Name Security Exchange Name Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Schedule of Impaired Loans by Class of Financing Receivable Impaired Financing Receivables [Table Text Block] Number of days past due Number Of Days Past Due Number Of Days Past Due Components of net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Financial Derivative Instruments Derivatives, Policy [Policy Text Block] Construction loans, maximum percent of capital Construction Loan Portfolio Maximum To Company Capital The regulatory maximum allowed ratio of loan portfolio to Company capital for construction loans. Net increase (decrease) in cash and cash equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect FDIC insurance premiums Federal Deposit Insurance Corporation Premium Expense Entity File Number Entity File Number Common Stock Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract] Equity compensation expense APIC, Share-based Payment Arrangement, Increase for Cost Recognition Class of Financing Receivable [Axis] Class of Financing Receivable [Axis] Home equity line of credit Home Equity Line of Credit Portfolio [Member] Home Equity Line of Credit Portfolio [Member] Impaired Financing Receivable, Recorded Investment [Abstract] Impaired Financing Receivable, Recorded Investment [Abstract] Interest and dividends on investments (includes tax-exempt income of $1,803,000 for March 31, 2022, $1,846,000 for December 31, 2021 and $1,956,000 for March 31, 2021) Interest and Dividend Income, Securities, Operating Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Amortization of identified intangibles Amortization of Intangible Assets Small Business Administration (SBA), CARES Act, Paycheck Protection Program 1 Small Business Administration (SBA), CARES Act, Paycheck Protection Program 1 [Member] Small Business Administration (SBA), CARES Act, Paycheck Protection Program 1 All Past Due Financial Asset, Past Due [Member] Loans Insured or Guaranteed by Government Authorities [Domain] Loans Insured or Guaranteed by Government Authorities [Domain] Certificates $250,000 and over Time Deposits 250000 Or More The aggregate amount of domestic or foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to more than $250,000. Fair Value (Estimated), Due in 1 to 5 years Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Defined contribution plan service period (in months) Deferred Compensation Arrangement with Individual, Requisite Service Period Delinquent period for loans charged off after receipt of notification Delinquent Period for Loans Charged Off, Period After Receipt of Notification from Bankruptcy Court Delinquent Period for Loans Charged Off, Period After Receipt of Notification from Bankruptcy Court Loans classified as TDRs that are involved in bankruptcy Financing Receivable, Loans Classified As Troubled Debt Restructurings That Are Involved In Bankruptcy Carrying amount of loans classified as troubled debt restructurings that are involved in bankruptcy as of the balance sheet date. Number of TDR loans involved in bankruptcy (loan) Financing Receivable, Modifications, Number Of Contracts Involved In Bankruptcy During Period Financing Receivable, Modifications, Number Of Contracts Involved In Bankruptcy During Period Accumulated amortization Accumulated Amortization Mortgage Servicing Rights The cumulative amount of amortization for mortgage servicing rights that has been recognized in the income statement. Cash Flow Hedging Cash Flow Hedging [Member] Proceeds from maturities, payments and calls of securities available for sale Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale Net unrealized loss on securities available for sale, net of taxes Net unrealized loss on securities available for sale, net of tax OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax Purchase of restricted equity securities Payments to Acquire Restricted Investments Award Type [Domain] Award Type [Domain] Award Type [Domain] 90+ Days Past Due Financial Asset, Equal to or Greater than 90 Days Past Due [Member] Share Repurchase Program [Domain] Share Repurchase Program [Domain] Loans used to collateralize borrowings from the Federal Home Loan Bank of Boston Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged Local Phone Number Local Phone Number Assets Assets [Abstract] Assets [Abstract] Proceeds from sales of other real estate owned Proceeds from Sale of Other Real Estate Fair Value, Measurements, Nonrecurring Fair Value, Nonrecurring [Member] Other Liabilities Other Liabilities [Member] Recorded investment, with related allowance Impaired Financing Receivable, with Related Allowance, Recorded Investment State and political subdivisions    State and political subdivisions US States and Political Subdivisions Debt Securities [Member] Interest Rate Swap February 12 2024 Interest Rate Swap February 12 2024 [Member] Interest Rate Swap February 12 2024 [Member] Financial Derivative Instruments Derivative Instruments and Hedging Activities Disclosure [Text Block] Schedule of Contractual Maturities of Investment Securities Investments Classified by Contractual Maturity Date [Table Text Block] Unpaid principal balance, with no related allowance Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance Grants during the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Schedule of Securities Gains and Losses Schedule of Realized Gain (Loss) [Table Text Block] Outstanding principal balance of loans serviced for others Residential Mortgage Loans Serviced For Others Outstanding Principal Dollar amount of principal outstanding on loans being serviced for others at the balance sheet date. Mortgage Servicing Rights Transfers and Servicing of Financial Assets [Text Block] Financing Receivable Allowance [Domain] Class of Financing Receivable [Domain] Cash dividend declared Dividends, Cash Discount rate Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate Retained earnings Retained Earnings [Member] Effect of one percentage point increase on accumulated benefit obligation Defined Benefit Plan, Effect of One Percentage Point Increase on Accumulated Postretirement Benefit Obligation Total deposits Deposits Financial Asset, Period Past Due [Domain] Financial Asset, Aging [Domain] Interest expense Interest Expense [Abstract] Certificates of Deposit Deposit Liabilities Disclosures [Text Block] Net gain on sale of other real estate owned Gains (Losses) on Sales of Other Real Estate Beginning balance Ending balance Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest Federal Reserve Bank Stock Federal reserve bank stock Federal Reserve Bank Stock Securities to be held to maturity, fair value Fair Value (Estimated) Securities to be held to maturity, Fair Value (Estimated) Securities to be held to maturity Debt Securities, Held-to-maturity, Fair Value Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Instruments and Hedging Activities Disclosure [Abstract] Charge offs Allowance for Loan and Lease Losses, Write-offs Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Pension expense Pension and Other Postretirement Benefits Cost (Reversal of Cost) Interest Rate Swap August 2 2024 Interest Rate Swap August 2 2024 [Member] Interest Rate Swap August 2 2024 [Member] Schedule of Accumulated Post-retirement Benefit Obligation and Funded Status Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block] Valuation allowance on impaired financing receivable Impaired Financing Receivable, Related Allowance, Measured at Fair Value Impaired Financing Receivable, Related Allowance, Measured at Fair Value Repurchase agreements Assets Sold under Agreements to Repurchase, Repurchase Liability Retirement Benefits, Description [Abstract] Retirement Benefits, Description [Abstract] Provision (credit) for loan losses Provision for loan losses Provision (credit) Provision for Loan and Lease Losses Fixed Rate Paid Derivative, Fixed Interest Rate Basic earnings per common share (usd per share) Basic EPS: Income available to common shareholders (usd per share) Earnings Per Share, Basic Gross realized losses Debt Securities, Realized Loss Debt Securities, Realized Loss 30-59 Days Past Due Financial Asset, 30 to 59 Days Past Due [Member] U.S. Government-sponsored agencies US Treasury and Government [Member] Interest and fees on loans (tax-exempt income) Interest Income and Fees on Loans Tax Exempt Interest Income and Fees on Loans Tax Exempt Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Loan maturities Loans and Leases Receivable, Term Loans and Leases Receivable, Term 90+ Days & Accruing Financing Receivable, 90 Days or More Past Due, Still Accruing National certificates of deposit National Certificates of Deposit The aggregate amount of national time deposits, including certificates of deposits, individual retirement accounts and open accounts. Amortized Cost, Due in 1 to 5 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five Other operating expense Other Noninterest Expense Number of loans placed on TDR status in previous 12 months Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts Expense related to 401(k) plan Defined Contribution Plan, Cost Fair Value Measurement [Domain] Fair Value Measurement [Domain] Schedule of Troubled Debt Restructurings on Financing Receivables Financing Receivable, Troubled Debt Restructuring [Table Text Block] Net increase in loans Payments to Acquire Finance Receivables Mortgage servicing rights capitalized Servicing Asset at Fair Value, Additions    Construction Construction Loans [Member] Net decrease in short-term borrowings Proceeds from (Repayments of) Short-term Debt Number of post-retirement benefit plans Number Of Post Retirement Benefit Plans Number of post-retirement benefit plans sponsored by the company. Restricted equity securities Federal Home Loan Bank Stock and Federal Reserve Bank Stock Gross realized gains Debt Securities, Realized Gain Debt Securities, Realized Gain Debt Securities, Held-to-maturity [Table] Debt Securities, Held-to-maturity [Table] Debit card income Debit Card [Member] Amortization of investment in limited partnership Other Depreciation and Amortization Non-interest income Noninterest Income [Abstract] Funded status Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] Impaired Financing Receivable, Average Recorded Investment [Abstract] Impaired Financing Receivable, Average Recorded Investment [Abstract] Related Allowance Impaired Financing Receivable, Related Allowance Consumer Consumer Portfolio Segment [Member] Fair value of securities transferred Available-for-Sale Securities, Transferred Security, at Fair Value Available-for-Sale, Transferred Security, at Fair Value Plan Name [Axis] Plan Name [Axis] Number of states Number Of States in New England Where FHLB Serve The number of States in New England where Federal Home Loan Bank do housing and financing services. Borrowed funds – long term Long-term Debt Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Total assets Assets, Fair Value Disclosure Level 1 Fair Value, Inputs, Level 1 [Member] Loans Insured or Guaranteed by Government Authorities [Axis] Loans Insured or Guaranteed by Government Authorities [Axis] Cash flows from investing activities Net Cash Provided by (Used in) Investing Activities [Abstract] Specific Reserves Financing Receivable, Recorded Investment, Greater than 30 Days Past Due, Placed in TDR in Previous 12 Months, Specific Allowance during Period Financing Receivable, Recorded Investment, Greater than 30 Days Past Due, Placed in TDR in Previous 12 Months, Specific Allowance during Period Net interest income after provision for loan losses Interest Income (Expense), after Provision for Loan Loss Other liabilities Other Liabilities Schedule of Past Due Loans Aging Financing Receivable, Past Due [Table Text Block] Income Tax Disclosure [Abstract] Income Tax Disclosure [Abstract] Entity Small Business Entity Small Business Loans classified as TDRs that are involved in foreclosure Loans Classified As Troubled Debt Restructurings That Are Involved In Foreclosure Loans Classified As Troubled Debt Restructurings That Are Involved In Foreclosure Allowance for Loan Losses by Class of Financing Receivable and Allowance Financing Receivable, Allowance for Credit Loss [Table Text Block]    Real estate Real Estate Loan [Member] Financial liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Total liabilities & shareholders' equity Liabilities and Equity Investments, Debt and Equity Securities [Abstract] Investments, Debt and Equity Securities [Abstract] Certificates of deposit Total certificates of deposit Local certificates of deposit Time Deposits Servicing assets and servicing liabilities at fair value, assumptions used to estimate fair value, discount rate adjustment factor (in hundredths) Servicing Assets And Servicing Liabilities At Fair Value Assumptions Used To Estimate Fair Value Discount Rate Adjustment Factor The amount of rate spread added to the ten-year US Treasury rate to derive the discount rate used in the fair value calculation for the loan servicing portfolio. Derivative Swap Type [Axis] Derivative Swap Type [Axis] Derivative Swap Type Amortized Cost, Due in 1 year or less Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, Year One Additional paid-in capital Additional Paid in Capital Derivative [Line Items] Derivative [Line Items] Interest rate swap agreements Interest Rate Swap [Member] Hedging Relationship [Domain] Hedging Relationship [Domain] 1 Strong Strong 1 [Member] Credit quality indicators that are developed and used internally by the company-level 1. Schedule of Financing Receivables [Line Items] Schedule of Financing Receivables [Line Items] -- None. No documentation exists for this element. -- Debt Securities, Held-to-maturity, Fair Value to Amortized Cost [Abstract] Debt Securities, Held-to-Maturity, Fair Value to Amortized Cost, after Allowance for Credit Loss [Abstract] Earnings Per Share Earnings Per Share [Text Block] Mortgage-backed securities    Mortgage-backed securities Collateralized Mortgage Backed Securities [Member] Entity Interactive Data Current Entity Interactive Data Current Accounting Changes and Error Corrections [Abstract] Accounting Changes and Error Corrections [Abstract] Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Certificates $100,000 to $250,000 Time Deposits Greater Than 100000 And Less Than 250000 The aggregate amount of domestic or foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to more than $100,000 but less than $250,000. Mortgage origination and servicing income, net of amortization Mortgage Banking [Member] Customer Loan Swaps Maturity Dates December 19, 2029 and October 1, 2039 Customer Loan Swaps Maturity Dates December 19, 2029 and April 1, 2039 [Member] Customer Loan Swaps Maturity Dates December 19, 2029 and April 1, 2039 [Member] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Reclassifications Reclassification, Comparability Adjustment [Policy Text Block] Amortization term (in years) Loans and Leases Receivable, Amortization Term Loans and Leases Receivable, Amortization Term Redemption of restricted equity securities Redemption Of Restricted Equity Securities Redemption of stock held at Federal Home Loan Bank of Federal Reserve Bank. Federal Home Loan Bank (FHLB) stock and Federal Reserve Bank Stock represents an equity interest in a FHLB of FRB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity). Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Unrealized Gains Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax Number of Loans Financing Receivable Modifications Number Of Contracts Greater Than 30 Days Past Due Place In TDR In Previous 12 Months The number of financing receivables greater than 30 days past due that have been modified by troubled debt restructurings and that have been placed in the TDR status in the previous 12 months. Effect of one percentage point increase on service cost Effect of One Percentage Point Increase on Service Cost Components The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the service cost components of net periodic postretirement health care benefit costs. Entity Address, State or Province Entity Address, State or Province Recognized interest income, with related allowance Impaired Financing Receivable, with Related Allowance, Interest Income, Cash Basis Method Fair Value (Estimated), Due after 10 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Loans classified as TDRs that were on non-accrual status Financing Receivable Loans Classified As Troubled Debt Restructurings That Were On Non Accrual Status Financing Receivable Loans , Classified As Troubled Debt Restructurings That Were On Non Accrual Status Schedule of Composition of Loan Portfolio Schedule Of Composition Of Loan Portfolio [Table Text Block] Tabular disclosure of the composition of loans contained in the loan portfolio. Fair Value (Estimated) (12 months or more) Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer Savings deposits Deposits, Savings Deposits Specific Reserves Troubled Debt Restructuring, Financing Receivable, Specific Allowance During Period Specific allowance for loan and lease losses on receivable financings that are classified as troubled debt restructurings during the period. Proceeds from sale of common stock Proceeds from sale of common stock Stock Issued During Period, Value, New Issues Recognized Interest Income Impaired Financing Receivable, Interest Income, Cash Basis Method Issuance of restricted stock Stock Issued During Period, Value, Restricted Stock Award, Gross Stock-Based Compensation Share-based Payment Arrangement [Text Block] Level 3 Fair Value, Inputs, Level 3 [Member] Other equity securities Equity Securities [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Net unrealized gain (loss) on securities available for sale AOCI, Debt Securities, Available-for-sale, Adjustment, after Tax Financing Receivable Information by Type of Reserve [Domain] Financing Receivable Information by Type of Reserve [Domain] Type of reserves based on individual impairment, historical loss experience, or qualitative factors. Proceeds from sale of common stock (in shares) Stock Issued During Period, Shares, New Issues TDR recorded investment more than 30 days past due Financing Receivable Recorded Investment Greater Than 30 Days Past Due Financing receivables that are greater than 30 days past due. Operating lease liability Operating Lease, Liability Document Transition Report Document Transition Report Common stock, one cent par value per share Common Stock, Value, Issued Remaining Term (In Years) Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Average recorded investment, with no related allowance Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment Current Financial Asset, Not Past Due [Member] Loans and Leases Receivable Disclosure [Abstract] Loans and Leases Receivable Disclosure [Abstract] Schedule of Estimated Fair Value of Financial Instruments Fair Value, by Balance Sheet Grouping [Table Text Block] Entity Emerging Growth Company Entity Emerging Growth Company Other real estate owned Other real estate owned Other Real Estate, Foreclosed Assets, and Repossessed Assets Accrued benefit cost at end of period Defined Benefit Plan, Funded (Unfunded) Status of Plan Period of temporary impairment Length Of Time Securities Temporarily Impaired Length of time securities are temporarily impaired. Restricted Stock Restricted Stock [Member] Receivables [Abstract] Receivables [Abstract] Investment Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Schedule of Allowance for Loan Losses Transactions Activity In Allowance For Loan Losses By Portfolio And Segment [Table Text Block] Tabular disclosure for the roll forward of change in allowance for loan losses from period to period and related loan balances. Cover [Abstract] Cover [Abstract] Assumed health care cost trend rate Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year Amortized Cost, Due in 1 to 5 years Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year One through Five Net gain Debt Securities, Gain (Loss) Income (Numerator) Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Net interest income Interest Income (Expense), Net Defined contribution plan employer maximum percentage match of annual salary based on employee contribution Defined Contribution Plan Employer Maximum Percentage Match Of Employee Annual Salary The highest percentage of employer match of employee contribution to defined contribution plan based on annual salary. 8 Doubtful Doubtful [Member] Pre-Modification Outstanding Recorded Investment Financing Receivable, Troubled Debt Restructuring, Premodification Schedule of Net Periodic Benefit Cost Not Yet Recognized Schedule of Net Periodic Benefit Cost Not yet Recognized [Table Text Block] Anticipated loan prepayment rate of servicing assets (in hundredths) Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Prepayment Speed Reserves for Qualitative Factors Reserve for Qualitative Factors [Member] Qualitative reserves judgmentally adjusted for local and national economic conditions, concentrations, portfolio composition, and other factors. Post-Modification Outstanding Recorded Investment Financing Receivable, Troubled Debt Restructuring, Postmodification Number of loans Financing Receivable Modifications Number Of Contracts Greater Than 30 Days Past Due Financing Receivable Modifications Number Of Contracts Greater Than 30 Days Past Due Financial Instrument [Axis] Financial Instrument [Axis] Fair Value (Estimated) Fair Value (Estimated) Debt Securities, Available-for-Sale, Excluding Accrued Interest Cash dividends declared (usd per share) Common Stock, Dividends, Per Share, Declared Accumulated Net Gain (Loss) on Securities Transferred from Available-for-Sale to Held-to-Maturity Accumulated Net Gain (Loss) on Securities Transferred from Available-for-Sale to Held-to-Maturity [Member] Accumulated Net Gain (Loss) on Securities Transferred from Available-for-Sale to Held-to-Maturity [Member] Change in net unrealized gain on available for sale securities, net of tax Transfer to Investments (Increase) decrease in interest-bearing deposits in other banks Interest-bearing Deposits in Other Banks Interest-bearing Deposits in Other Banks Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] Dividends paid Payments of Dividends Loans Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Schedule of Available For Sale, Held-to-Maturity, and Restricted Equity Securities Schedule of Available For Sale Held to Maturity and Restricted Equity Securities [Table Text Block] Tabular presentation of available for sale securities, held-to-maturity securities and restricted equity securities as of the balance sheet date. Carrying value Reported Value Measurement [Member] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Equity [Abstract] Equity [Abstract] Consumer loans, loan to value percent, minimum Collateralized Consumer Loans To Individuals Loan To Value Collateralized Consumer Loans To Individuals Loan To Value Document Quarterly Report Document Quarterly Report Financing Receivable, Troubled Debt Restructuring [Table] Financing Receivable, Troubled Debt Restructuring [Table] Unrealized Losses Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss Receive Fixed, Pay Variable Receive Fixed, Pay Variable [Member] Receive Fixed, Pay Variable Fair Value (Estimated) (Less than 12 months) Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months Delinquent period before consumer loans are charged off Delinquent Period Before Consumer Loans Charged Off Delinquent Period Before Consumer Loans Charged Off Unpaid Principal Balance Impaired Financing Receivable, Unpaid Principal Balance Recorded investment, with no related allowance Impaired Financing Receivable, with No Related Allowance, Recorded Investment TDR recorded investment Balance Financing Receivable, Troubled Debt Restructuring Recoveries Allowance for Loan and Lease Loss, Recovery of Bad Debts Construction loans and non-owner-occupied commercial real estate loans, percent of capital Construction And Non Owner Occupied Commercial Real Estate Loans Portfolio To Company Capital The actual ratio of loan amount to Company capital for construction and non-owner-occupied commercial real estate. Financial Asset, Period Past Due [Axis] Financial Asset, Aging [Axis] Debt Securities, Available-for-sale [Line Items] Debt Securities, Available-for-sale [Line Items] Municipal Municipal Portfolio [Member] Class of loans receivable which are related to municipalities or other city governments. Fair Value (Estimated), Due in 1 to 5 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Unrealized Losses Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax Hedging Designation [Axis] Hedging Designation [Axis] Increase (Decrease) in Accumulated Other Comprehensive Income [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Document Fiscal Year Focus Document Fiscal Year Focus Equity compensation expense Share-based Payment Arrangement, Noncash Expense Accumulated Other Comprehensive Income (Loss) [Roll Forward] AOCI Attributable to Parent, Net of Tax [Roll Forward] Unpaid principal balance with related allowance Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance Depreciation Depreciation Allowance for Loan Losses Allowance for Credit Losses [Text Block] Related deferred taxes Related deferred taxes Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Impaired Financing Receivable, Unpaid Principal Balance [Abstract] Impaired Financing Receivable, Unpaid Principal Balance [Abstract] Collateral [Domain] Collateral Held [Domain] Purchases of securities available for sale Payments to Acquire Debt Securities, Available-for-sale Number of loans Number of Loans Financing Receivable, Modifications, Number of Contracts Derivative notional amount Derivative, Notional Amount Interest Rate Swap April 07 2023 Interest Rate Swap April 07 2023 [Member] Interest Rate Swap April 07 2023 Other Assets Other Assets [Member] Net securities gains Net gain on sale or call of securities Debt and Equity Securities, Gain (Loss) Net loans Financing Receivable, after Allowance for Credit Loss Benefits paid Defined Benefit Plan, Benefit Obligation, Benefits Paid 2010 Plan Plan 2010 [Member] A stock option plan approved by shareholders at the 2010 annual meeting to attract and retain the best available personnel, provide additional incentive to officers, employees and non-employee directors and promote the success of its business. Net increase (decrease) in other liabilities Increase (Decrease) in Other Operating Liabilities Schedule of Certificates of Deposit Time Deposits [Table Text Block] The tabular disclosure of the breakdown of the balance of time deposits. Capital expenditures Payments to Acquire Property, Plant, and Equipment Fair Value Derivative, Fair Value, Net General Reserves on Loans Based on Historical Loss Experience General Reserves Based on Historical Loss Experience [Member] General reserves for types of portfolios of loans based on historical loss experience. Fair Value (Estimated), Due in 1 to 5 years Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five Share-based Payment Arrangement [Abstract] Share-based Payment Arrangement [Abstract] Related income taxes Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Total liabilities Liabilities Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Fair value of mortgage servicing rights Mortgage servicing rights Servicing Asset at Fair Value, Amount Award Type [Axis] Award Type [Axis] Cash flows from financing activities Net Cash Provided by (Used in) Financing Activities [Abstract] Total shareholders' equity Balance at beginning of period Balance at end of period Stockholders' Equity Attributable to Parent Mortgage servicing rights Mortgage Servicing Rights Gross Gross amount, as of the balance sheet date, of mortgage servicing rights. Number of classes in the commercial loan portfolio Financing Receivable, Commercial, Number of Loan Classes Financing Receivable, Commercial, Number of Loan Classes Schedule of Securities Temporarily Impaired Schedule of Temporary Impairment Losses, Investments [Table Text Block] Number of shares issued (in shares) Common Stock, Shares, Issued Service charges on deposit accounts Deposit Account [Member] City Area Code City Area Code Capital Purchase Program Capital Purchase Program [Member] Capital Purchase Program [Member] Net unrealized loss, net of taxes on transferred securities Available-for-sale Securities, Transferred to Held-to-maturity Securities, Accumulated Unrealized Gain (Loss) Available-for-sale Securities, Transferred to Held-to-maturity Securities, Accumulated Unrealized Gain (Loss) Designated as Hedging Instrument Designated as Hedging Instrument [Member]    Other Other Loans [Member] Other Loans Securities to be held to maturity (fair value of $353,191,000 at March 31, 2022, $375,327,000 at December 31, 2021 and $388,836,000 at March 31, 2021) Amortized Cost Debt Securities, Held-to-Maturity, Excluding Accrued Interest, before Allowance for Credit Loss Entity Address, City or Town Entity Address, City or Town Ending balance collectively evaluated for impairment Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment Delinquent period for loans charged off Delinquent Period for Loans Charged Off Delinquent Period for Loans Charged Off Unrealized Gains Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain Payment to repurchase common stock Payments for Repurchase of Common Stock Shareholders' equity Stockholders' Equity Attributable to Parent [Abstract] Interest Rate Swap April 07 2024 Interest Rate Swap April 07 2024 [Member] Interest Rate Swap April 07 2024 Schedule of Accumulated Other Comprehensive Income (Loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Non-cash transactions Noncash Investing and Financing Items [Abstract] Allowance for loan losses as a percent of total loans Allowance for Loan Losses of Total Loans, Percentage Allowance for Loan Losses of Total Loans, Percentage Net increase in certificates of deposit Increase (Decrease) in Time Deposits Balance Sheet Location [Axis] Balance Sheet Location [Axis] Other Comprehensive Income (Loss) Comprehensive Income (Loss) Note [Text Block] Measurement Frequency [Domain] Measurement Frequency [Domain] Proceeds from sales and transfers of loans Proceeds from Sale of Loans Held-for-sale      Total interest expense Interest Expense Risk rated loans receivable Commercial And Municipal Risk Rated Loans Receivable Loans subject to review and validation annually by independent consulting firm as well internal credit review function.      Total interest income Interest and Dividend Income, Operating Net periodic benefit cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) 60-89 Days Past Due Financial Asset, 60 to 89 Days Past Due [Member] Net unrealized gain on postretirement costs Net unrecognized postretirement benefits included in accumulated other comprehensive income Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract] Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract] Customer loan interest swap agreements Customer Loan Interest Swap [Member] Customer Loan Interest Swap [Member] Retained earnings Retained Earnings (Accumulated Deficit) Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Entity Filer Category Entity Filer Category Defined contribution plan, employer matching contribution, percent of match Defined Contribution Plan, Employer Matching Contribution, Percent of Match Interest on borrowed funds Interest Expense, Borrowings Share Repurchase Program [Axis] Share Repurchase Program [Axis] Income Statement [Abstract] Income Statement [Abstract] Tangible book value per common share (usd per share) Tangible Book Value Per Common Share Tangible book value of common stock per share. Total Fair Value Estimate of Fair Value Measurement [Member] Entity Registrant Name Entity Registrant Name Number of derivative instruments Derivative, Number of Instruments Held Allowance for Loan and Lease Losses [Roll Forward] Allowance for Loan and Lease Losses [Roll Forward] Securities to be held to maturity Debt Securities, Held-to-maturity, Maturity [Abstract] Nonaccrual loans Financing Receivable, Nonaccrual Impaired loans Impaired Loans Fair Value Disclosure This element represents the fair value disclosure of impaired loans that have had a fair value adjustment since their initial recognition. Impact of Recently Issued Accounting Standards Accounting Standards Update and Change in Accounting Principle [Text Block] Investment management and fiduciary income Fiduciary and Trust [Member] Issuance of restricted stock (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Income tax expense Income Tax Expense (Benefit)    Term Term Loan [Member] The catagory of loans which are designated to individuals for a residence that typically includes traditional amortizing home mortgages. Amendment Flag Amendment Flag Amortization of mortgage servicing rights Amortization of Mortgage Servicing Rights (MSRs) Commercial Commercial Portfolio Segment [Member] Percent of related loans Allowance for Loan and Lease Losses, Related Loans, Percentage Allowance for Loan and Lease Losses, Related Loans, Percentage Amortized Cost Debt Securities, Available-for-Sale, Amortized Cost, Excluding Accrued Interest, after Allowance for Credit Loss Equity Components [Axis] Equity Components [Axis] Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Net unrealized gain on transferred securities, net of taxes Net unrealized gain on securities transferred from available for sale to held to maturity, net of tax Available-for-sale Securities, Transferred to Held-to-maturity Securities, Unrealized Gain (Loss) Available-for-sale Securities, Transferred to Held-to-maturity Securities, Unrealized Gain (Loss) Entity Tax Identification Number Entity Tax Identification Number Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Increase (decrease) in qualitative portion Allowance for Loan and Lease Losses, Related Loans, Period Increase (Decrease) Allowance for Loan and Lease Losses, Related Loans, Period Increase (Decrease) 2020 Plan 2020 Equity Incentive Plan [Member] 2020 Equity Incentive Plan Document Fiscal Period Focus Document Fiscal Period Focus Accumulated Net Gain (Loss) from Cash Flow Hedges Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Shares not issued (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Schedule of Stock by Class [Table] Schedule of Stock by Class [Table] Payment to repurchase common stock Stock Repurchased During Period, Value Interest and fees on loans (includes tax-exempt income of $291,000 for March 31, 2022, $271,000 for December 31, 2021 and $290,000 for March 31, 2021) Interest and Fee Income, Loans and Leases Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Fair Value Fair Value Measurement, Policy [Policy Text Block] Unrecognized transition obligation for postretirement benefits, net of taxes Other Comprehensive Income (Loss), Defined Benefit Plan, Transition Asset (Obligation), Reclassification Adjustment from AOCI, after Tax Number of classes in the residential loan portfolio Loans and Leases Receivable, Residential, Number of Loan Classes Loans and Leases Receivable, Residential, Number of Loan Classes Furniture and equipment expense Equipment Expense Product and Service [Axis] Product and Service [Axis] Fair Value, Recurring and Nonrecurring [Table] Fair Value, by Balance Sheet Grouping [Table] Federal Home Loan Bank advances Long-term Federal Home Loan Bank Advances New Accounting Pronouncements and Changes in Accounting Principles [Abstract] Accounting Standards Update and Change in Accounting Principle [Abstract] 7 Substandard Substandard [Member] Percent of total allowance reserve Percentage of Total Reserve Allowance accounted for by Loan Loss Allowances Percentage of Total Reserve Allowance accounted for by Loan Loss Allowances Equity Component [Domain] Equity Component [Domain] Payment to repurchase common stock (in shares) Stock Repurchased During Period, Shares 2 Above Average Above Average 2 [Member] Credit quality indicators that are developed and used internally by the company-level 2. Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] 5 Watch Watch 5 [Member] Credit quality indicators that are developed and used internally by the company-level 5. Statement [Line Items] Statement [Line Items] Delinquent period before residential loans are placed on non-accrual status Delinquent Period Before Residential Loans Placed On Non Accrual Status The minimum amount of days past due at which residential loans are placed on non-accrual status.. Loan-to-value percent, commercial real estate Commercial Real Estate Loans Maximum Loan To Value The maximum percentage of loan to value for commercial real estate loans based on current appraisal information. Net unrealized gain on cash flow hedging derivative instruments Net unrealized gain on cash flow hedging derivative instruments, net of tax Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Net loss on disposal of premises and equipment Gain (Loss) on Disposition of Property Plant Equipment, Excluding Oil and Gas Property and Timber Property Schedule of Risk Ratings for Loans Financing Receivable Credit Quality Indicators [Table Text Block] Post-retirement benefit plan health insurance subsidy range minimum per month per person Post Retirement Benefit Plan Health Insurance Subsidy Range Minimum The minimum amount employer will contribute per month to post-retiree for subsidizing the cost of health care insurance. NOW deposits Deposits, Negotiable Order of Withdrawal (NOW) Securities available for sale Available-for-sale Securities, Debt Maturities [Abstract] Liabilities Liabilities [Abstract] Loan to value ratio Loans and Leases Receivable, Loan to Value Ratio Loans and Leases Receivable, Loan to Value Ratio Securities available for sale Debt Securities, Available-for-sale Loans originated for resale Payments for Origination of Mortgage Loans Held-for-sale Specific Reserves on Loans Evaluated Individually for Impairment Specific Reserves Evaluated Individually for Impairment [Member] Specific reserved based on evaluating each loan individually. Net acquisition amortization Amortization of Acquisition Costs Unallocated Unallocated Financing Receivables [Member] Income before income taxes Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Level 2 Fair Value, Inputs, Level 2 [Member] Non-interest expense Noninterest Expense [Abstract] Federal Home Loan Bank Stock FHLB stock investment Federal Home Loan Bank Stock Recorded Investment Impaired Financing Receivable, Recorded Investment Fair Value (Estimated) Debt Securities, Available-for-sale, Unrealized Loss Position Fair Value (Estimated), Due in 1 year or less Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Employee Benefit Plans Retirement Benefits [Text Block] Interest Rate Swap February 12 2023 Interest Rate Swap February 12 2023 [Member] Interest Rate Swap February 12 2023 [Member] Schedule of Basic and Diluted Earnings per Share (EPS) Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Interest and dividends on investments (tax-exempt income) Interest Income, Securities, Operating, Tax Exempt Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Schedule of Assets Measured on Nonrecurring Basis Measured at Fair Value Fair Value Measurements, Nonrecurring [Table Text Block] Vesting [Axis] Vesting [Axis] Title of 12(b) Security Title of 12(b) Security Proceeds from sale of common stock Proceeds from Issuance of Common Stock Total assets Assets Plan Name [Domain] Plan Name [Domain] Number of shares authorized (in shares) Common Stock, Shares Authorized Interest paid Interest Paid, Excluding Capitalized Interest, Operating Activities Diluted EPS: Income available to common shareholders plus assumed conversions Net Income (Loss) Available to Common Stockholders, Diluted Basic EPS: Income available to common shareholders Net Income (Loss) Available to Common Stockholders, Basic Percentage of loans receivable, by type Percentage of Financing Receivable, By Type Reflects the break down of the gross carrying amount of all categories of loans and leases held in the portfolio, after deducting deferred income, but before deducting the allowance for losses on loans and leases as a percentage of total portfolio. Document Type Document Type Schedule of Nonvested Restricted Stock Units Activity Schedule of Nonvested Restricted Stock Units Activity [Table Text Block] Product and Service [Domain] Product and Service [Domain] Other real estate owned, valuation allowance Real Estate Owned, Valuation Allowance Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Derivative Contract [Domain] Derivative Contract [Domain] 3 Satisfactory Satisfactory 3 [Member] Credit quality indicators that are developed and used internally by the company-level 3. Impairment reserve Mortgage servicing rights impairment Servicing Asset at Amortized Cost, Other than Temporary Impairments Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Fair Value by Measurement Frequency [Axis] Measurement Frequency [Axis]      Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Borrowed funds – short term Short-term Debt Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items]      Total non-interest income Noninterest Income Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Notional Amount Derivative Liability, Notional Amount Transfers and Servicing [Abstract] Transfers and Servicing [Abstract] Basic EPS: Income available to common shareholders (in shares) Weighted Average Number of Shares Outstanding, Basic Residential Residential Portfolio Segment [Member] Diluted earnings per common share (usd per share) Diluted EPS: Income available to common shareholders plus assumed conversions (usd per share) Earnings Per Share, Diluted Interest bearing deposits in other banks Interest-bearing Deposits in Banks and Other Financial Institutions Demand deposits Demand Deposit Accounts Effect of dilutive securities: restricted stock (in shares) Weighted Average Number Diluted Shares Outstanding Adjustment Vesting [Domain] Vesting [Domain] Hedging Relationship [Axis] Hedging Relationship [Axis] Unamortized net actuarial gain Defined Benefit Plan, Accumulated Other Comprehensive Income (Loss), Gain (Loss), before Tax Impairment losses Restricted Equity Securities Unrealized Losses As of the balance sheet date, the excess of carrying value (amortized cost) over fair value of a security categorized as non marketable securities, exclusive of dividend or interest income recognized but not yet received and exclusive of any write-downs for other-than-temporary impairment. Such item represents the gross unrecognized holding loss. Comprehensive income (loss) Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Attributable to Parent Unallocated Reserves Unallocated Reserves [Member] Additional reserves not fitting the other criterias. Net cash provided by financing activities Net Cash Provided by (Used in) Financing Activities Other comprehensive income (loss) net of tax Other Comprehensive Income (Loss), Net of Tax [Abstract] Shares (Denominator) Weighted Average Number of Shares Outstanding, Diluted [Abstract] Vesting Term (In Years) Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Moving average of weekly prepayment data (in months) Moving Average Of Weekly Prepayment Data The moving average period of weekly prepayment data used as assumption in evaluating the carrying value of mortgage servicing rights. Corporate securities Corporate Debt Securities [Member] Fair Value Fair Value Disclosures [Text Block] Collateral [Axis] Collateral Held [Axis] Schedule of Assets and Liabilities Measured on Recurring Basis Measured at Fair Value Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Fair Value (Estimated), Due after 10 years Debt Securities, Held-to-Maturity, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 10 Net increase (decrease) in demand, savings, and money market accounts Increase (Decrease) in Demand Deposits, Savings Deposits, and Money Market Accounts Increase (Decrease) in Demand Deposits, Savings Deposits, and Money Market Accounts Accumulated other comprehensive income (loss) AOCI Attributable to Parent [Member] Other assets Other Assets Number of shares outstanding (in shares) Beginning balance (in shares) Ending balance (in shares) Common Stock, Shares, Outstanding Financial Instruments [Domain] Financial Instruments [Domain] Derivative [Table] Derivative [Table] Fair Value (Estimated), Due in 1 to 5 years Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year 5 Through 10 Estimated plan expense Defined Benefit Plan, Expected Future Employer Contributions, Remainder of Fiscal Year Interest income Interest and Dividend Income, Operating [Abstract] Document Period End Date Document Period End Date Deferred tax expense Accumulated Other Comprehensive Income Defined Benefit Plans Tax, Deferred Tax Benefit Tax effects of the increase (decrease) to accumulated comprehensive income during the period related to benefit plans. Five Years Five Years [Member] Equity-based compensation plans that vest in five years. Entity Central Index Key Entity Central Index Key 2021 Year Awarded 2021 [Member] Year Awarded 2021 Money market deposits Deposits, Money Market Deposits Unrealized losses arising during the period Unrealized gains on cash flow hedging derivatives arising during the period OCI, before Reclassifications, before Tax, Attributable to Parent Construction loans and non-owner-occupied commercial real estate loans, maximum percent of capital Construction And Non Owner Occupied Commercial Real Estate Loans Maximum Loan Portfolio To Company Capital The regulatory maximum allowed ratio of loan portfolio to Company capital for construction and non-owner-occupied commercial real estate. Recognized interest income, with no related allowance Impaired Financing Receivable, with No Related Allowance, Interest Income, Cash Basis Method Schedule of Held-to-maturity Securities [Line Items] Schedule of Held-to-maturity Securities [Line Items] One Year One Year [Member] One Year [Member] Award Date [Domain] Award Date [Domain] Mortgage loans in the process of foreclosure Mortgage Loans in Process of Foreclosure, Amount Debt Securities, Available-for-sale [Table] Debt Securities, Available-for-sale [Table] Amortized Cost, Due in 1 year or less Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One Ending balance specifically evaluated for impairment Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment Premises and equipment, net Property, Plant and Equipment, Net Accrued interest receivable Interest Receivable Effect of one percentage point increase on interest cost Effect of One Percentage Point Increase on Interest Cost Components The effect of a one-percentage-point increase in the assumed health care cost trend rates on the aggregate of the interest cost components of net periodic postretirement health care benefit costs. Book value per common share (usd per share) Book Value Per Common Share Book value of common stock per share. Number of securities temporarily impaired (security) Number Of Securities Temporarily Impaired The number of securities with unrealized losses, classified as temporarily impaired, held in a Company's portfolio as of the balance sheet date. Benefit obligation at beginning of year Benefit obligation at end of period Benefit obligation at end of period Defined Benefit Plan, Benefit Obligation Interest on deposits with other banks Interest Income, Deposits with Financial Institutions Loans held for sale Financing Receivable, Held-for-Sale, Not Part of Disposal Group, after Valuation Allowance Interest Rate Swap June 28 2021 Interest Rate Swap June 28 2021 [Member] Interest Rate Swap June 28 2021 [Member] Trading Symbol Trading Symbol Carrying value Servicing Asset at Amortized Cost, Fair Value Earnings Per Share [Abstract] Earnings Per Share [Abstract] Repayment on long-term borrowings Repayments of Other Long-term Debt Derivative assets Derivative Asset Three Years Three Years [Member] Equity-based compensation plans that vest in three years. Ending balance specifically evaluated for impairment Financing Receivable, Individually Evaluated for Impairment Number of loan classes Financing Receivables, Number Of Loan Classes Financing Receivables, Number Of Loan Classes Unrealized Losses Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss Net (increase) decrease in other assets and accrued interest Increase (Decrease) in Other Operating Assets Net unrealized loss on cash flow hedging derivative instruments AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax Proceeds from sales of securities available for sale Proceeds from Sale of Debt Securities, Available-for-sale Deposits [Abstract] Certificates of deposit less than $100,000 Time Deposits, Less than $100,000 Total borrowed funds Debt and Lease Obligation Compensation expense recognized for restricted shares Share-based Payment Arrangement, Expense Residential loans, loan to value percent minimum Residential Loans Typical Loan To Value Range Low Residential Loans Typical Loan To Value Range Low 4 Average Average 4 [Member] Credit quality indicators that are developed and used internally by the company-level 4. Entity Current Reporting Status Entity Current Reporting Status Per-Share Amount Earnings Per Share, Basic and Diluted [Abstract] Outstanding loans and commitments subject by independent consulting firm Outstanding Loans And Commitments Subject By Independent Consulting Firm Percentage of loans and commitments subject to review by an independent consulting firm each year. Salaries and employee benefits Labor and Related Expense Other operating income Noninterest Income, Other Operating Income Net amortization of premiums on investments Accretion (Amortization) of Discounts and Premiums, Investments Proceeds from sales of securities Proceeds from Sale and Maturity of Marketable Securities Cash and cash equivalents Cash and cash equivalents at beginning of period      Cash and cash equivalents at end of period Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Schedule of Derivative Instruments Schedule of Derivative Instruments [Table Text Block] Number of mortgage loans in the process of foreclosure Mortgage Loans in Process of Foreclosure, Number Mortgage Loans in Process of Foreclosure, Number Proceeds from maturities, payments, calls and sales of securities to be held to maturity Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities Common stock par value (usd per share) Common Stock, Par or Stated Value Per Share Pay Fixed, Receive Variable Pay Fixed, Receive Variable [Member] Pay Fixed, Receive Variable Post-retirement benefit plan health insurance subsidy range maximum per month per person Post Retirement Benefit Plan Health Insurance Subsidy Range Maximum The maximum amount employer will contribute per month to post-retiree for subsidizing the cost of health care insurance. Purchases of securities to be held to maturity Payments to Acquire Held-to-maturity Securities 2018 Year Awarded 2018 [Member] Year Awarded 2018 [Member] Number of shares of common stock reserved for issuance (in shares) Common Stock, Capital Shares Reserved for Future Issuance Award Date [Axis] Award Date [Axis] Interest Rate Swap June 28 2026 Interest Rate Swap June 28 2026 [Member] Interest Rate Swap June 28 2026 [Member] Derivative, gain on derivative Derivative, Gain on Derivative Financing Receivable, Troubled Debt Restructuring [Line Items] Financing Receivable, Troubled Debt Restructuring [Line Items] Securities pledged as collateral Debt Securities, Available-for-sale, Restricted Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Reclassification of net realized gains during the period Amortization of net unrealized gains Reclassification from AOCI, Current Period, before Tax, Attributable to Parent      Total non-interest expense Noninterest Expense Entity Address, Postal Zip Code Entity Address, Postal Zip Code Interest Rate Swap March 13 2030 Interest Rate Swap March 13 2030 [Member] Interest Rate Swap March 13 2030 [Member] Diluted EPS: Income available to common shareholders plus assumed conversions (in shares) Weighted Average Number of Shares Outstanding, Diluted Fair Value, Measurements, Recurring Fair Value, Recurring [Member] Income Taxes Income Tax Disclosure [Text Block] Common Stock Stockholders' Equity Note Disclosure [Text Block] Schedule of Nonaccrual Loans Financing Receivable, Nonaccrual [Table Text Block] Schedule of Net Pension Costs Schedule of Net Benefit Costs [Table Text Block] Measurement Basis [Axis] Measurement Basis [Axis] Average recorded investment, with related allowance Impaired Financing Receivable, with Related Allowance, Average Recorded Investment Net deferred loan costs included in loan balances Loans and Leases Receivable, Deferred Income Number of loans Number of Loans Financing Receivable Modifications Number Of Contracts During Period The number of financing receivables that have been modified by troubled debt restructurings during the current period. Fair Value of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Total share based compensation cost Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Recognized And Not yet Recognized Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Recognized And Not yet Recognized Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Loans Loans Receivable, Fair Value Disclosure Unfunded, supplemental retirement benefits payable period Post Employment Plan, Supplemental Benefits, Payment Period Upon Retirement Or Death Post Employment Plan, Supplemental Benefits, Payment Period Upon Retirement Or Death Class of Stock [Line Items] Class of Stock [Line Items] Balance Financing Receivable Recorded Investment Greater Than30 Days Past Due Placed In T D R In Previous12 Months Financing receivables that are greater than 30 days past due and that had been placed in TDR status in the previous 12 months. Occupancy expense Occupancy, Net Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Entity Address, Address Line One Entity Address, Address Line One      Net cash used by investing activities Net Cash Provided by (Used in) Investing Activities Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] Change in benefit obligation Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Cash flows from operating activities Net Cash Provided by (Used in) Operating Activities [Abstract] Entity Shell Company Entity Shell Company 2022 Year Awarded 2022 [Member] Year Awarded 2022 Amortized Cost, Due in 5 to 10 years Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year Five through Ten Amortized cost Servicing Asset at Amortized Cost Non-interest income Revenue from Contract with Customer, Including Assessed Tax Average Recorded Investment Impaired Financing Receivable, Average Recorded Investment Current Fiscal Year End Date Current Fiscal Year End Date Loans Ending balance Financing Receivable, before Allowance for Credit Loss Reclassifications Disclosure of Reclassification Amount [Text Block] Accrued pension liability Liability, Defined Benefit Pension Plan Interest Rate Swap March 13 2025 Interest Rate Swap March 13 2025 [Member] Interest Rate Swap March 13 2025 [Member] Residential loans, loan to value percent, maximum Residential Loans Typical Loan To Value Residential Loans Typical Loan To Value Amortized Cost, Due after 10 years Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss, Maturity, Allocated and Single Maturity Date, after Year 10 Statement [Table] Statement [Table] Specific Reserves Troubled Debt Restructuring, Financing Receivable, Specific Allowance Specific allowance for loan and lease losses on receivable financings that are classified as troubled debt restructurings. Asset-backed securities Asset-backed Securities [Member] Impact of Recently Issued Accounting Standards New Accounting Pronouncements, Policy [Policy Text Block] Unrecognized compensation costs Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount Consumer loans, loan to value percent, maximum Collateralized Consumer Loans To Individuals Loan To Value Maximum Range High Collateralized Consumer Loans To Individuals Loan To Value Maximum Range High Stockholders' Equity [Abstract] Stockholders' Equity Note [Abstract] Stockholders' Equity Note [Abstract] Less allowance for loan losses Allowance for loan losses Financing Receivable, Allowance for Credit Loss Goodwill Goodwill Financing Receivable Information by Type of Reserve [Axis] Financing Receivable Information by Type of Reserve [Axis] Type of reserves based on individual impairment, historical loss experience, or qualitative factors. Amortized Cost, Due after 10 years Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year 10 Derivative Swap Type [Domain] Derivative Swap Type [Domain] Derivative Swap Type Interest Rate Swap June 27 2021 Interest Rate Swap June 27 2021 [Member] Interest Rate Swap June 27 2021 [Member] 2010 and 2020 Equity Incentive Plan 2010 and 2020 Equity Incentive Plan [Member] 2010 and 2020 Equity Incentive Plan Number of loans classified as TDRs that were on non-accrual status Financing Receivable Number Of Loans Classified As Troubled Debt Restructurings That Were On Non Accrual Status The number of loans classified as troubled debt restructurings that were on non-accrual status as of the balance sheet date. Unrealized Losses (Less than 12 months) Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss Number of securities temporarily impaired for twelve months or more (security) Number Of Securities Temporarily Impaired Twelve Months The number of securities temporarily impaired as of the balance sheet date for a period of 12 months or more. Interest Rate Swap August 5 2024 Interest Rate Swap August 5 2024 [Member] Interest Rate Swap August 5 2024 [Member] Loans Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss Adjustments to reconcile net income to net cash provided by operating activities Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Fair Value (Estimated), Due in 1 year or less Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One Commercial, construction and home equity loans used to collateralize unused line of credit at the Federal Reserve Bank of Boston Loans Pledged as Collateral 6 OAEM OAEM 6 [Member] Credit quality indicators that are developed and used internally by the company-level 6. Expected future benefit payments, current year Defined Benefit Plan, Expected Future Benefit Payment, Remainder of Fiscal Year Net gain on sales of loans Gain (Loss) on Sales of Loans, Net Reconciliation of Mortgage Servicing Assets Reconciliation of Mortgage Servicing Rights [Table Text Block] A tabular presentation of the net mortgage servicing rights as of the balance sheet date. Unrealized Losses (12 months or more) Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Change in deferred taxes Deferred Income Tax Expense (Benefit) Common stock and additional paid-in capital Common Stock Including Additional Paid in Capital [Member] Schedule of Financing Receivables [Table] Schedule of Financing Receivables [Table] -- None. No documentation exists for this element. -- 2020 Year Awarded 2020 [Member] Year Awarded 2020 [Member]