Statement of Financial Position [Abstract] Allowance for loan losses, loans receivable Loans and Leases Receivable, Allowance Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Common stock, shares authorized (in shares) Common Stock, Shares Authorized Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Investments, Debt and Equity Securities [Abstract] SECURITIES Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Banking and Thrift [Abstract] Amount available for the payment of dividends Statutory Accounting Practices, Statutory Amount Available for Dividend Payments with Regulatory Approval Demand and NOW Demand Deposit Accounts Regular savings Deposits, Savings Deposits Money markets Deposits Money Market And Investment Savings Deposits Deposits money market and investment savings deposits. Time deposits Time Deposits Total deposits Deposits Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Components of Other Assets Schedule of Other Assets [Table Text Block] BORROWINGS Federal Home Loan Bank Advances And Stock And Other Borrowings Disclosure [Text Block] Federal Home Loan Bank Advances And Stock And Other Borrowings Disclosure [Text Block] Property, Plant and Equipment [Abstract] Premises and Equipment Property, Plant and Equipment [Table Text Block] Earnings Per Share [Abstract] Schedule of Basic and Diluted Net Income Per Share Schedule of Weighted Average Number of Shares [Table Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Measurement Frequency [Axis] Measurement Frequency [Axis] Fair Value, Measurement Frequency [Domain] Fair Value, Measurement Frequency [Domain] Recurring Fair Value, Measurements, Recurring [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value, Inputs, Level 1 [Member] Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Significant Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Securities or Other Assets Sold under Agreements to Repurchase [Axis] Securities or Other Assets Sold under Agreements to Repurchase [Axis] Assets Sold under Agreements to Repurchase, Type [Domain] Assets Sold under Agreements to Repurchase, Type [Domain] U.S. Government and government-sponsored enterprise obligations US Government Corporations and Agencies Securities [Member] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Government-sponsored residential mortgage-backed securities Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] Government-sponsored commercial mortgage-backed securities Government Sponsored Commercial Mortgage Backed Securities [Member] Government sponsored commercial mortgage backed securities. Marketable equity securities Equity Securities [Member] Mortgage servicing rights Mortgage Loan Servicing Rights [Member] Mortgage Loan Servicing Rights [Member] Interest rate swaps Interest Rate Swap [Member] Asset Class [Axis] Asset Class [Axis] Asset Class [Domain] Asset Class [Domain] Government-sponsored residential collateralized debt obligations US Government-sponsored Enterprises Debt Securities [Member] Government-sponsored commercial collateralized debt obligations Government Sponsored Commercial Collateralized Debt Obligations [Member] Government sponsored commercial collateralized debt obligations. Asset-backed securities Asset-backed Securities [Member] Corporate debt securities Corporate Debt Securities [Member] Obligations of states and political subdivisions US States and Political Subdivisions Debt Securities [Member] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Domain] Mortgage Loans on Real Estate, Loan Type [Domain] Mortgage Loan Derivative Assets & Liabilities Conventional Mortgage Loan [Member] 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] Available for sale securities Available-for-sale Securities Mortgage loan derivative assets Derivative Asset Mortgage loan derivative liabilities Derivative Liability Loans held for sale Loans Receivable Held-for-sale, Amount Mortgage servicing rights Servicing Asset at Fair Value, Amount Interest rate swap assets Interest Rate Derivative Assets, at Fair Value Interest rate swap liabilities Interest Rate Derivative Liabilities, at Fair Value Regulatory Capital Amounts and Ratios Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Reconciliation of Company's Total Consolidated Equity to Capital Amounts Reconciliation Of Companys And Banks Stockholders Equity To Regulatory Capital Table [Table Text Block] Reconciliation Of Companys And Banks Stockholders Equity To Regulatory Capital Table [Text Block] Goodwill and Intangible Assets Disclosure [Abstract] GOODWILL AND CORE DEPOSIT INTANGIBLES Goodwill and Intangible Assets Disclosure [Text Block] Summary of Deposits Schedule Of Components Of Deposits By Type Table [Table Text Block] Schedule of components of deposits by type. Summary of Contractual Maturities of Time Deposits Schedule Of Contractual Maturities Of Time Deposits Table [Table Text Block] Schedule of contractual maturities of time deposits. Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Number of Stock Options (shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Outstanding at December 31, 2015 (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Forfeited, expired or canceled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Outstanding at December 31, 2016 (in shares) Stock options vested and exercisable at December 31, 2016 (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Number Stock Options, Weighted- Average Exercise Price (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Outstanding at December 31, 2015 (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Exercised (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Forfeited or expired (usd per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Outstanding at December 31, 2016 (usd per share) Stock options vested and exercisable at December 31, 2016 (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract] Weighted Average Remaining Contractual Term, Outstanding at December 31, 2016 Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted Average Remaining Contractual Term, Stock options vested and exercisable at December 31, 2016 Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Aggregate Intrinsic Value, Exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Aggregate Intrinsic Value, Outstanding at December 31, 2016 Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Aggregate Intrinsic Value, Stock options vested and exercisable at December 31, 2016 Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Receivables [Abstract] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Class of Financing Receivable, Type [Axis] Class of Financing Receivable, Type [Axis] Class of Financing Receivable, Type [Domain] Class of Financing Receivable, Type [Domain] Troubled Debt Restructurings Troubled Debt Restructurings [Member] Troubled Debt Restructurings [Member] Financing Receivable, Modifications [Line Items] Financing Receivable, Modifications [Line Items] Impaired Financing Receivable, Recorded Investment [Abstract] Impaired Financing Receivable, Recorded Investment [Abstract] Accrual status Financing Receivable, Recorded Investment, Current Non-accrual status Financing Receivable, Recorded Investment, Nonaccrual Status Total recorded investment in TDRs Financing Receivable, Modifications, Recorded Investment Accruing TDRs performing under modified terms more than one year Tdr Loans Performing In Accordance With Restructured Terms For More Than One Year Tdr Loans Performing In Accordance With Restructured Terms For More Than One Year Specific reserves for TDRs included in the balance of allowance for loan losses Allowance For Loan And Lease Losses Related To Troubled Debt Restructurings Allowance For Loan And Lease Losses Related To Troubled Debt Restructurings Additional funds committed to borrowers in TDR status Additional Funds Committed To Borrowers In Troubled Debt Restructuring Status Additional Funds Committed To Borrowers In Troubled Debt Restructuring Status Income Tax Disclosure [Abstract] Deferred tax assets: Components of Deferred Tax Assets [Abstract] Deferred tax assets: Deferred Tax Assets, Net of Valuation Allowance [Abstract] Loans Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses Investment security losses Deferred Tax Assets, Investments Net unrealized losses on securities available for sale Deferred Tax Assets, Unrealized Losses on Available-for-Sale Securities, Gross Net unrealized losses on interest rate swaps Deferred Tax Assets, Derivative Instruments Pension, deferred compensation and post-retirement liabilities Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Postretirement Benefits Stock incentive award plan Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost Deposits - purchase accounting adjustment Deferred Tax Assets, Deposits, Purchase Accounting Adjustments Deferred Tax Assets, Deposits, Purchase Accounting Adjustments Accrued expenses Deferred Tax Assets, Accrued Expenses Deferred Tax Assets, Accrued Expenses Tax attributes Deferred Tax Assets, Tax Credit Carryforwards Other Deferred Tax Assets, Other Gross deferred tax assets Deferred Tax Assets, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Gross deferred tax assets, net of valuation allowance Deferred Tax Assets, Net of Valuation Allowance Deferred tax liabilities: Components of Deferred Tax Liabilities [Abstract] Other purchase accounting adjustments Deferred Tax Liabilities Purchase Accounting Adjustment Deferred Tax Liabilities Purchase Accounting Adjustment Other Deferred Tax Liabilities, Other Gross deferred tax liabilities Deferred Tax Liabilities, Gross Net deferred tax asset Deferred Tax Assets, Net Nonrecurring Fair Value, Measurements, Nonrecurring [Member] Impaired loans Impaired Loans Fair Value Disclosure Impaired loans fair value disclosure. Other real estate owned Other Real Estate Owned Fair Value Disclosure Other real estate owned fair value disclosure. Total Assets, Fair Value Disclosure Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table] Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Table] Federal Home Loan Bank, Advances, Option [Axis] Federal Home Loan Bank, Advances, Option [Axis] Federal Home Loan Bank, Advances, Option [Domain] Federal Home Loan Bank, Advances, Option [Domain] Federal Home Loan Bank, Advances, Callable Option Federal Home Loan Bank, Advances, Callable Option [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Wholesale Reverse Repurchase Agreements Wholesale Reverse Repurchase Agreements [Member] Wholesale Reverse Repurchase Agreements [Member] Retail Repurchase Agreements Retail Repurchase Agreements [Member] Retail Repurchase Agreements [Member] Subordinated Notes Due October 2024 Subordinated Notes Due October 2024 [Member] Subordinated Notes Due October 2024 [Member] Brokered Sweep Deposit Brokered Deposits [Member] Brokered Deposits [Member] Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Subordinated Debt Subordinated Debt [Member] Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] Fair Value, Option, Qualitative Disclosures Related to Election [Line Items] Advances from FHLBB Long-term Federal Home Loan Bank Advances Fair value adjustment on FHLBB advances acquired in the Merger Federal Home Loan Bank, Advances, Valuation Adjustments under Fair Value Option Number of advances Number Of Advances Number of advances. Federal home loan bank advances interest rate at period end Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Interest Rate at Period End Estimated eligible collateral value Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged Unused line of credit Federal Home Loan Bank, Advances, General Debt Obligations, Amount of Available, Unused Funds Additional borrowings Line Of Credit Facility Additional Borrowing Capacity Line of credit facility additional borrowing capacity. Percent of aggregate principal amount Threshold Percentage Of Investment In Capital Stock Based On Aggregate Unpaid Principal Amount Threshold Percentage Of Investment In Capital Stock Based On Aggregate Unpaid Principal Amount. Borrowings from the FHLBB (percent) Investment In Capital Stock As Percentage Of Federal Home Loan Bank Advances Investment In Capital Stock As Percentage of Federal Home Loan Bank Advances. Federal Home Loan Bank Stock Federal Home Loan Bank Stock Other borrowings Other Borrowings Number of individual borrowings, wholesale reverse purchase agreements Number Of Borrowings, Wholesale Reverse Purchase Agreements Number Of Borrowings, Wholesale Reverse Purchase Agreements Wholesale reverse repurchase agreements, remaining term Debt Instrument Remaining Term Debt Instrument Remaining Term Weighted average cost (percent) Debt, Weighted Average Interest Rate Subordinated notes, face amount Debt Instrument, Face Amount Subordinated notes, stated interest rate Debt Instrument, Interest Rate, Stated Percentage Subordinated notes, carrying value Long-term Debt Junior subordinated debt, face amount Subordinated Debt Fair value acquisition discount Debt Instrument, Unamortized Discount Basis spread on variable rate Debt Instrument, Basis Spread on Variable Rate Percentage of other borrowings at cost Debt Instrument, Interest Rate, Effective Percentage Borrowings acquired in the Merger Transfers Accounted for as Secured Borrowings, Associated Liabilities, Carrying Amount Number of transfers Transfers Accounted for as Secured Borrowings, Number of Transfers Transfers Accounted for as Secured Borrowings, Number of Transfers Number of leased bank branches Number Of Leased Bank Branches Number Of Leased Bank Branches Capital lease obligations Capital Lease Obligations Other borrowings Brokered Deposit Brokered Deposit Number of counterparties to unused federal funds lines of credit Number Of Counterparties, Lines Of Credit Number Of Counterparties, Lines Of Credit Unused federal funds lines of credit Line of Credit Facility, Maximum Borrowing Capacity Contractual Maturities and Weighted-Average Rates of Outstanding Advances Schedule of Federal Home Loan Bank, Advances, by Branch of FHLB Bank [Table Text Block] Schedule of Repurchase Agreements Schedule of Repurchase Agreements [Table Text Block] Compensation and Retirement Disclosure [Abstract] Schedule of Defined Benefit Plans Disclosures [Table] Schedule of Defined Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Defined Benefit Plan and Other Postretirement Benefit Plan [Domain] Qualified Pension Plan Pension Plan [Member] Supplemental Executive Retirement Plans Supplemental Employee Retirement Plan [Member] Other Post - Retirement Benefits Other Postretirement Benefit Plan [Member] Defined Benefit Plan Disclosure [Line Items] Defined Benefit Plan Disclosure [Line Items] 2017 Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months 2018 Defined Benefit Plan, Expected Future Benefit Payments, Year Two 2019 Defined Benefit Plan, Expected Future Benefit Payments, Year Three 2020 Defined Benefit Plan, Expected Future Benefit Payments, Year Four 2021 Defined Benefit Plan, Expected Future Benefit Payments, Year Five Years 2022-2026 Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter Income Statement [Abstract] Interest and dividend income: Interest and Dividend Income, Operating [Abstract] Loans Interest and Fee Income, Loans and Leases Securities-taxable interest Interest Income, Securities, Operating, Taxable Securities-non-taxable interest Interest Income, Securities, Operating, Tax Exempt Securities-dividends Dividend Income, Operating Interest-bearing deposits Interest Income, Deposits with Financial Institutions Total interest and dividend income Interest and Dividend Income, Operating Interest expense: Interest Expense [Abstract] Deposits Interest Expense, Deposits Borrowed funds Interest Expense, Borrowings Total interest expense Interest Expense Net interest income (expense) Interest Income (Expense), Net Provision for loan losses Provision for Loan and Lease Losses Net interest income after provision for loan losses Interest Income (Expense), after Provision for Loan Loss Non-interest income: Noninterest Income [Abstract] Service charges and fees Bank Servicing Fees Income from mortgage banking activities Gain (Loss) on Sales of Loans, Net Bank-owned life insurance income Bank Owned Life Insurance, Including Income From Death Benefit Bank Owned Life Insurance, Including Income From Death Benefit Gain on sales of securities, net Gain (Loss) on Sale of Securities, Net Net loss on limited partnership investments Income (Loss) From Limited Partnership Investments, Net Of Tax Income (Loss) From Limited Partnership Investments, Net Of Tax Other income (loss) Non Interest Income Expense Other Non Interest Income Expense Other Total non-interest income Noninterest Income Non-interest expense: Noninterest Expense [Abstract] Salaries and employee benefits Labor and Related Expense Occupancy and equipment Occupancy, Net Service bureau fees Service Bureau Fees Service bureau fees. Professional fees Professional Fees Marketing and promotions Marketing and Advertising Expense FDIC insurance assessments Federal Deposit Insurance Corporation Premium Expense Core deposit intangible amortization Amortization of Intangible Assets Merger related expense Payment For Merger Related Costs Payment for Merger Related Costs FHLBB prepayment penalties Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Repayment and Penalties Other Other Noninterest Expense Total non-interest expense Noninterest Expense Income before income taxes Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Provision (benefit) for income taxes Income Tax Expense (Benefit) Net income Net Income (Loss) Attributable to Parent Net income per share: Earnings Per Share, Basic and Diluted [Abstract] Basic (usd per share) Earnings Per Share, Basic Diluted (usd per share) Earnings Per Share, Diluted Weighted-average shares outstanding: Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic (in shares) Weighted Average Number of Shares Outstanding, Basic Diluted (in shares) Weighted Average Number of Shares Outstanding, Diluted Net unrealized gain (loss) on securities available for sale Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax Net unrealized gain (loss) on securities available for sale, income taxes (benefit) Accumulated Other Comprehensive Income (Loss), Available For Sale Securities Adjustment, Tax Accumulated Other Comprehensive Income (Loss), Available For Sale Securities Adjustment, Tax Accumulated other comprehensive income (loss) Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax Encumbered securities Encumbered Securities Encumbered securities. Fair value pledged for derivative collateral Trading Securities Pledged as Collateral Estimated fair value of obligations of states and political subdivisions Estimated Fair Value Of Obligations Of States And Political Subdivisions Estimated Fair Value Of Obligations Of States And Political Subdivisions General obligation bonds General Obligation Bonds General obligation bonds. Obligations of political subdivisions Obligations Of Political Subdivisions Obligations of political subdivisions. Available-for-sale securities with unrealized losses, less than twelve months Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year Unrealized losses equaling cost basis for less than twelve months (percent) Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Aggregate Losses As Percentage Of Cost Basis Available for sale securities continuous unrealized loss position less than twelve months aggregate losses as percentage of cost basis. Securities with unrealized losses for twelve months or more Securities In Unrealized Loss Positions, Qualitative Disclosure, Number Of Positions, Greater Than Or Equal To One Year Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater Than or Equal to One Year Unrealized losses equaling cost basis for twelve months or more (percent) Securities In Unrealized Loss Position, Twelve Months Or More Aggregate Losses As Percentage Of Cost Basis Securities In Unrealized Loss Position, Twelve Months Or More Aggregate Losses As Percentage Of Cost Basis Number of issues had unrealized losses for less than twelve months Securities In Unrealized Loss Positions, Qualitative Disclosure, Number Of Positions, Less Than One Year Securities In Unrealized Loss Positions, Qualitative Disclosure, Number Of Positions, Less Than One Year Number of issues had unrealized losses for twelve months or more Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year Individual unrealized loss that represent an other than temporary impairment Other than Temporary Impairment Losses, Investments Number of pooled trust securities Number Of Pooled Trust Securities Number Of Pooled Trust Securities Yield on security Yield Rate On Investment Securities Yield rate on investment securities. Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Commercial real estate loans Commercial Real Estate Portfolio Segment [Member] Commercial business loans Commercial Portfolio Segment [Member] Consumer loans Consumer Portfolio Segment [Member] Owner occupied Owner Occupied Real Estate Loan [Member] Owner Occupied Real Estate Loan [Member] Investor non-owner occupied Investor Real Estate Loan [Member] Investor Real Estate Loan [Member] Construction Commercial Construction Loans [Member] Commercial Construction Loans [Member] Commercial business loans Commercial Loan [Member] Residential real estate Residential Real Estate Loan [Member] Residential Real Estate Loan [Member] Home equity Home Equity Loan [Member] Residential construction Residential Construction Loans [Member] Residential Construction Loans [Member] Other consumer Other Consumer Loan [Member] Other Consumer Loan [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Loans Receivable Concentration Risk Loans Receivable Concentration Risk [Member] Loans Receivable Concentration Risk [Member] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Loans Receivable Loans Receivable [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Total loans Loans and Leases Receivable, Gross Percent of total loans Concentration Risk, Percentage Net deferred loan costs and premiums Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums Allowance for loan losses Loans - net Loans and Leases Receivable, Net Amount RESTRICTIONS ON CASH AND DUE FROM BANKS Restricted Assets Disclosure [Text Block] REGULATORY MATTERS Regulatory Capital Requirements under Banking Regulations [Text Block] Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Retained Earnings Retained Earnings [Member] Statement [Line Items] Statement [Line Items] Dividends declared/ paid per common share (usd per share) Common Stock, Dividends, Per Share, Declared Anti-dilutive options excluded from earnings per share calculation (in shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Condensed Financial Information of Parent Company Only Disclosure [Abstract] PARENT COMPANY FINANCIAL INFORMATION Condensed Financial Information of Parent Company Only Disclosure [Text Block] INCOME TAXES Income Tax Disclosure [Text Block] Commitments and Contingencies Disclosure [Abstract] Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2017 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2018 Operating Leases, Future Minimum Payments, Due in Two Years 2019 Operating Leases, Future Minimum Payments, Due in Three Years 2020 Operating Leases, Future Minimum Payments, Due in Four Years 2021 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Future minimum rental commitments under the terms of leases Operating Leases, Future Minimum Payments Due Commercial real estate loans and consumer Commercial Real Estate and Consumer Portfolio Segment [Member] Commercial Real Estate and Consumer Portfolio Segment [Member] Construction Construction Loans [Member] Number of Contracts Financing Receivable, Modifications, Number of Contracts Pre-Modification Outstanding Recorded Investment Financing Receivable, Modifications, Pre-Modification Recorded Investment Post-Modification Outstanding Recorded Investment Financing Receivable, Modifications, Post-Modification Recorded Investment Schedule of Finite-Lived Intangible Assets, Future Amortization Expense Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block] Schedule of Impaired Financing Receivable [Table] Schedule of Impaired Financing Receivable [Table] Unallocated Unallocated Financing Receivables [Member] Receivables Acquired with Deteriorated Credit Quality [Axis] Receivables Acquired with Deteriorated Credit Quality [Axis] Receivables Acquired with Deteriorated Credit Quality [Domain] Receivables Acquired with Deteriorated Credit Quality [Domain] Receivables acquired with deteriorated credit quality Receivables Acquired with Deteriorated Credit Quality [Member] Financing Receivable, Allowance for Credit Losses [Line Items] Financing Receivable, Allowance for Credit Losses [Line Items] Allowance related to loans individually evaluated and deemed impaired Impaired Financing Receivable, Related Allowance Allowance related to loans collectively evaluated and not deemed impaired Financial Receivables Not Deemed To Be Impaired Related Allowance Financial Receivables Not Deemed To Be Impaired Related Allowance. Allowance related to loans acquired with deteriorated credit quality Financing Receivable, Allowance for Credit Losses Total allowance for loan losses Loans deemed impaired Impaired Financing Receivable, Recorded Investment Loans not deemed impaired Financing Receivable Not Deemed To Be Impaired Recorded Investment Financing receivable not deemed to be impaired recorded investment. Loans acquired with deteriorated credit quality Financing Receivable, Net Total loans Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] Change in Benefit Obligation: Defined Benefit Plan, Change in Benefit Obligation [Roll Forward] Benefit obligation at beginning of year Defined Benefit Plan, Benefit Obligation Service cost Defined Benefit Plan, Service Cost Interest cost Defined Benefit Plan, Interest Cost Plan participants’ contributions Defined Benefit Plan, Contributions by Plan Participants Actuarial loss (gain) Defined Benefit Plan, Actuarial Gain (Loss) Benefits paid and administration expenses Defined Benefit Plan, Benefits Paid Curtailments, settlements, special termination benefits Defined Benefit Plan Curtailments Settlements Special Termination Benefits Changes Benefit Obligation Defined Benefit Plan Curtailments Settlements Special Termination Benefits Changes Benefit Obligation Benefit obligation at end of year Change in Plan Assets: Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward] Fair value of plan assets at beginning of year Defined Benefit Plan, Fair Value of Plan Assets Actual return (loss) on plan assets Defined Benefit Plan, Actual Return on Plan Assets Employer contributions Defined Benefit Plan, Contributions by Employer Settlements Defined Benefit Plan, Settlements, Plan Assets Fair value of plan assets at end of year Funded Status: Defined Benefit Plan, Funded Status of Plan [Abstract] Underfunded status at end of year Defined Benefit Plan, Funded Status of Plan Amounts Recognized in the Consolidated Statements of Condition Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract] Accrued expenses and other liabilities Defined Benefit Plan, Amounts Recognized in Balance Sheet 2017 Time Deposit Maturities, Next Twelve Months 2018 Time Deposit Maturities, Year Two 2019 Time Deposit Maturities, Year Three 2020 Time Deposit Maturities, Year Four 2021 Time Deposit Maturities, Year Five Contractual maturities of time deposits, Total Future Minimum Rental Commitments Under Terms of Leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Future Minimum Rental Receivable Under Non-Cancelable Leases Schedule Of Future Minimum Payments Receivable For Operating Leases Table [Table Text Block] Schedule of future minimum payments receivable for operating leases. Financial Instruments Contract Amounts Represent Credit Risk Schedule of Fair Value, Off-balance Sheet Risks [Table Text Block] Accounting Policies [Abstract] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Net Gain From Sales of Loans Net Gain From Sales of Loans [Member] Net Gain From Sales of Loans [Member] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] Mortgage loans held for sale Gains (Losses) In Fair Value, Mortgage Loans Held For Sale Gains (Losses) In Fair Value, Mortgage Loans Held For Sale Schedule of Assets Sold under Agreements to Repurchase [Table] Schedule of Assets Sold under Agreements to Repurchase [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] US Treasury and Government US Treasury and Government [Member] Securities or Other Assets Sold under Agreements to Repurchase, Maturity Periods [Axis] Repurchase Agreements and Similar Transactions, Maturity Periods [Axis] Assets Sold under Agreements to Repurchase, Maturity Period [Domain] Repurchase Agreements and Similar Transactions, Maturity Periods [Domain] Overnight Maturity Overnight [Member] Up to 1 Year Maturity Up To 1 Year [Member] Maturity Up To 1 Year [Member] 1 - 3 Years Maturity 1 to 3 Years [Member] Maturity 1 to 3 Years [Member] Greater than 3 Years Maturity Greater Than 3 Years [Member] Maturity Greater Than 3 Years [Member] Assets Sold under Agreements to Repurchase [Line Items] Assets Sold under Agreements to Repurchase [Line Items] Borrowings under repurchase agreements Securities Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement Quarterly Financial Information Disclosure [Abstract] Severance costs Severance Costs Merger related expenses Payments for Merger Related Costs Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Summary Of Significant Accounting Policies [Table] Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate [Domain] Real Estate [Domain] Residential Real Estate Residential Real Estate [Member] Commercial Real Estate Commercial Real Estate [Member] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Summary Of Significant Accounting Policies [Line Items] Number of wholly-owned subsidiaries Number Of Wholly-Owned Subsidiaries Number Of Wholly-Owned Subsidiaries Other real estate owned Other Real Estate, Foreclosed Assets, and Repossessed Assets Number of banking offices Number Of Banking Offices Number of banking offices. Number of ATMs Number Of Automated Teller Machines Number of automated teller machines. Stock's quoted market value Federal Home Loan Bank Stock Quoted Market Value Federal home loan bank stock quoted market value. Period after termination of membership in FHLBB that must pass before stock is redeemable Federal Home Loan Bank Stock, Period After Termination of Membership That Must Pass Before Stock is Redeemable Federal Home Loan Bank Stock, Period After Termination of Membership That Must Pass Before Stock is Redeemable Impairment charges Impairment Charges For Federal Home Loan Bank Stock Impairment charges for federal home loan bank stock. Loan payments days Number Of Loan Payment Term Past Due Number of loan payment term past due. Period of continuous payments for non-accrual loans to be restored to accrual status Period Of Continuous Payments Received For Non-Accrual Loans To Be Restored To Accrual Status Period of Continuous Payments Received for Non-Accrual Loans to be Restored to Accrual Status Historical loss factor number of years Historical Loss Factor, Number Of Years Historical Loss Factor, Number Of Years Collateral dependent days Period Which Impairment Evaluation Likely To Happen Period which impairment evaluation likely to happen. Recognition period of losses on open and closed end consumer loans Loans And Leases Receivable, Losses On Open And Closed End Loans, Recognition Period Loans and Leases Receivable, Losses on Open and Closed End Loans, Recognition Period Number of days before which impairment evaluation is likely to happen Period Before Which Impairment Evaluation Likely To Happen Period before which impairment evaluation likely to happen. Commercial real estate property Period For Commercial Real Estate Property Loan Impaired Period for commercial real estate property loan impaired. BOLI limit with any individual carrier, as percentage of capital plus reserves (percent) Bank Owned Life Insurance With Individual Carrier as Percentage of Capital Plus Reserves Bank Owned Life Insurance With Individual Carrier as Percentage of Capital Plus Reserves Premises and equipment, estimated useful life Property, Plant and Equipment, Useful Life Write-downs of long-lived assets were recorded for any period presented Impairment of Long-Lived Assets Held-for-use Goodwill impairment during period Goodwill, Impairment Loss Uncertain tax positions Liability for Uncertainty in Income Taxes, Current Eligible age required for the benefits Minimum Age Of Eligible Participants For Life Insurance And Postretirement Health Care Benefits Description Minimum Age Of Eligible Participants For Life Insurance And Postretirement Health Care Benefits Description Minimum years of service for the benefits Minimum Years Of Service Of Eligible Participants For Life Insurance And Postretirement Health Care Benefits Description Minimum Years Of Service Of Eligible Participants For Life Insurance And Postretirement Health Care Benefits Description Purchased Credit Impaired Loans Purchased Credit Impaired Loans [Member] Purchased Credit Impaired Loans [Member] Purchased Accounting Adjustments for Purchased Credit Impaired Loans Certain Loans Acquired in Transfer Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward] Balance at beginning of period Certain Loans Acquired in Transfer Accounted for as Debt Securities, Purchased Accounting Adjustments, Accretable and Nonaccretable Yield Certain Loans Acquired in Transfer Accounted for as Debt Securities, Purchased Accounting Adjustments, Accretable and Nonaccretable Yield Acquisition Certain Loans Acquired In Transfer Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Additions Certain Loans Acquired In Transfer Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Additions Accretion Certain Loans Acquired In Transfer Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Accretion Certain Loans Acquired In Transfer Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Accretion Paid off Certain Loans Acquired In Transfer Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Loans Paid Certain Loans Acquired In Transfer Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Loans Paid Reclassification to accretable Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Reclassifications To Nonaccretable Difference Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Purchased Accounting Adjustments, Accretable And Nonaccretable Yield, Reclassifications To Nonaccretable Difference Balance at end of period Effective Income Tax Rate Reconciliation, Amount [Abstract] Provision for income tax at statutory rate Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Increase (decrease) resulting from: Effective Income Tax Rate Reconciliation, Percent [Abstract] State income taxes, net of federal benefit Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Increase in cash surrender value of bank-owned life insurance Income Tax Reconciliation Increase In Cash Surrender Value Of Bank Owned Life Insurance Income tax reconciliation increase in cash surrender value of bank owned life insurance. Dividend received deduction Effective Income Tax Rate Reconciliation, Deduction, Dividends, Amount Tax exempt interest and disallowed interest expense Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Employee Stock Ownership Plan Income Tax Reconciliation Employee Stock Ownership Plan Income Tax Reconciliation Employee Stock Ownership Plan Nondeductible acquisition costs Effective Income Tax Rate Reconciliation, Nondeductible Expense, Acquisition Costs, Amount Effective Income Tax Rate Reconciliation, Nondeductible Expense, Acquisition Costs, Amount Excess parachute payments Effective Income Tax Rate Reconciliation, Nondeductible Expense, Excess Parachute Payments, Amount Effective Income Tax Rate Reconciliation, Nondeductible Expense, Excess Parachute Payments, Amount Investment tax credits Effective Income Tax Rate Reconciliation, Tax Credit, Investment, Amount Other, net Effective Income Tax Rate Reconciliation, Other Reconciling Items, Amount Total income tax expense (benefit) Effective income tax rate (benefit) Effective Income Tax Rate Reconciliation, Percent Business Combinations [Abstract] Schedule of Business Acquisitions, by Acquisition [Table] Schedule of Business Acquisitions, by Acquisition [Table] Business Acquisition [Axis] Business Acquisition [Axis] Business Acquisition, Acquiree [Domain] Business Acquisition, Acquiree [Domain] Legacy United Legacy United [Member] Legacy United [Member] Entity by Location [Axis] Entity by Location [Axis] Location [Domain] Location [Domain] Express Drive-Up Drive Up Office [Member] Drive Up Office [Member] Loan Production Offices Loan Production Office [Member] Loan Production Office [Member] Loans At Acquisition Date [Line Items] Business Acquisition [Line Items] Acquired common shares outstanding, percentage Business Acquisition, Percentage of Voting Interests Acquired Number of branch location Number Of Branch Locations Number Of Branch Locations Shares issued to acquiree entity (in shares) Conversion of Stock, Shares Issued Total consideration paid at closing Business Combination, Consideration Transferred Closing price of the common share (usd per share) Business Acquisition, Share Price Servicing Asset at Amortized Cost [Table] Servicing Asset at Amortized Cost [Table] Servicing Asset at Amortized Cost [Line Items] Servicing Asset at Amortized Cost [Line Items] Mortgage servicing rights: Servicing Asset at Amortized Cost, Balance [Roll Forward] Balance at beginning of year Servicing Asset at Amortized Cost Issuances/additions Servicing Asset at Amortized Cost, Additions Change in fair value recognized in income Servicing Asset At Amortized Value Gain (Loss) Recognized In Net Income Servicing Asset at Amortized Value Gain (Loss) Recognized in Net Income Balance at end of year Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Restricted Stock Restricted Stock [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Aggregate fair value of vested options Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Granted, weighted average grant date fair value (usd per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value Share-based compensation Share-based Compensation Compensation cost not yet recognized Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Cost not yet recognized, period for recognition Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Unvested restricted stock expected year one (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Number Of Shares Expected To Vest With In One Year Share Based Compensation Arrangement By Share Based Payment Award, Equity Instruments Other Than Options, Number of Shares Expected to Vest With in One Year Number. Unvested restricted stock expected year two (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Number Of Shares Expected To Vest With In Two Years Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Expected To Vest With in Two Year Number. Unvested restricted stock expected year three (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Number Of Shares Expected To Vest With In Three Years Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Number of Shares Expected to Vest With in Three Years Unvested restricted stock expected year four (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Number Of Shares Expected To Vest With In Four Years Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Number of Shares Expected to Vest With in Four Years Unvested restricted stock expected year five (in shares) Share-Based Compensation Arrangement By Share-Based Payment Award, Equity Instruments Other Than Options, Number Of Shares Expected To Vest With In Five Years Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other Than Options, Number of Shares Expected to Vest With in Five Years Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Parent Company Parent Company [Member] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] Assets: Assets [Abstract] Cash and due from banks Cash and Due from Banks Investment in United Bank Investment In Related Parties Investment in related parties. Due from United Bank Due from Related Parties Other assets Other Assets Total Assets Assets Liabilities and Stockholders’ Equity: Liabilities and Equity [Abstract] Subordinated debentures Accrued expenses and other liabilities Accrued Expenses And Other Liabilities Accrued expenses and other liabilities. Stockholders’ equity Stockholders' Equity Attributable to Parent Total Liabilities and Stockholders’ Equity Liabilities and Equity DEPOSITS Deposit Liabilities Disclosures [Text Block] Nature of Operations and Financial Statement Presentation Basis of Accounting, Policy [Policy Text Block] Common Share Repurchases Stockholders' Equity, Policy [Policy Text Block] Cash and Cash Equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Securities Marketable Securities, Policy [Policy Text Block] Derivative Financial Instruments Derivatives, Methods of Accounting, Hedge Effectiveness [Policy Text Block] Derivative Loan Commitments Loan Commitments, Policy [Policy Text Block] Forward Loan Sale Commitments Forward Loan Sale Commitments Policy [Policy Text Block] Forward loan sale commitments. Federal Home Loan Bank Stock Federal Home Loan Bank Stock Policy [Policy Text Block] federal home loan bank stock. Loans Held For Sale Finance, Loan and Lease Receivables, Held-for-sale, Policy [Policy Text Block] Loans Finance, Loans and Leases Receivable, Policy [Policy Text Block] Interest and Fees on Loans Interest And Fees On Loans Policy [Policy Text Block] Interest and fees on loans. Allowance for Loan Losses Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Servicing Transfers and Servicing of Financial Assets, Servicing of Financial Assets, Policy [Policy Text Block] Other Real Estate Owned Other Real Estate Owned Valuation Allowance Policy [Policy Text Block] Other real estate owned valuation allowance. Bank-Owned Life Insurance Life Insurance Bank Owned Policy [Policy Text Block] Life insurance bank owned policy. Transfers of Financial Assets Transfers and Servicing of Financial Assets, Transfers of Financial Assets, Policy [Policy Text Block] Premises and Equipment Property, Plant and Equipment, Policy [Policy Text Block] Marketing and Promotions Advertising Costs, Policy [Policy Text Block] Impairment of Long-Lived Assets Other Than Goodwill Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block] Goodwill Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Investments in Limited Partnerships Equity Method Investments, Policy [Policy Text Block] Pension and Other Post-Retirement Benefits Pension and Other Postretirement Plans, Policy [Policy Text Block] Fair Values of Financial Instruments Fair Value of Financial Instruments, Policy [Policy Text Block] Earnings per Common Share Earnings Per Share, Policy [Policy Text Block] Employee Stock Ownership Plan Compensation Related Costs, Policy [Policy Text Block] Share-Based Compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Off-balance Sheet Financial Instruments Off Balance Sheet Financial Instruments Policy [Policy Text Block] Off Balance Sheet Financial Instruments Policy [Text Block] Segment Information Segment Reporting, Policy [Policy Text Block] Recent Accounting Pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Schedule of Financing Receivable, Recorded Investment, Credit Quality Indicator [Table] Schedule of Financing Receivable, Recorded Investment, Credit Quality Indicator [Table] Internal Credit Assessment [Axis] Internal Credit Assessment [Axis] Internal Credit Assessment [Domain] Internal Credit Assessment [Domain] Loans rated 1 — 5 Pass [Member] Loans rated 6 Special Mention [Member] Loans rated 7 Substandard [Member] Loans rated 8 Doubtful [Member] Loans rated 9 Unlikely to be Collected Financing Receivable [Member] Financing Receivable, Recorded Investment [Line Items] Financing Receivable, Recorded Investment [Line Items] Total real estate loans Available for Sale Securities Available-for-sale Securities [Member] Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] Balance at beginning of period Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value Purchases Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases Principal payments and net accretion Fair Value Measurement With Unobservable Inputs Reconciliation, Recurring Basis, Assets, Principal Payments And Net Accretion Fair Value Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Assets, Principal Payments and Net Accretion Total realized losses on sales included in income / Change in fair value recognized in income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings Total unrealized gains (losses) included in other comprehensive income Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss) Issuances Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Issuances Balance at end of period Schedule Of Available For Sale And Held To Maturity Securities [Table] Schedule Of Available For Sale And Held To Maturity Securities [Table] Schedule of available for sale and held to maturity securities. Investment Type [Axis] Investment Type [Axis] Investments [Domain] Investments [Domain] Total debt securities Debt Securities [Member] Schedule Of Available For Sale And Held To Maturity Securities [Line Items] Schedule Of Available For Sale And Held To Maturity Securities [Line Items] Schedule of available for sale and held to maturity securities. Available for sale: Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] Less than 12 months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 12 Months or More Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Total Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Unrealized Loss Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] Less than 12 months Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 12 Months or More Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss Held to Maturity: Held-to-maturity Securities, Continuous Unrealized Loss Position [Abstract] Fair Value Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] Less than 12 months Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 12 Months or More Held-to-maturity Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Total Held-to-maturity Securities, Continuous Unrealized Loss Position, Fair Value Unrealized Loss Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss [Abstract] Less than 12 months Held-to-maturity Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 12 Months or More Held-to-maturity Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total Held-to-maturity Securities, Continuous Unrealized Loss Position, Accumulated Loss New Accounting Pronouncements or Change in Accounting Principle [Table] New Accounting Pronouncements or Change in Accounting Principle [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2016-09, Excess Tax Benefit Component Accounting Standards Update 2016-09, Excess Tax Benefit Component [Member] Accounting Standards Update 2016-09, Excess Tax Benefit Component [Member] Scenario [Axis] Scenario [Axis] Scenario, Unspecified [Domain] Scenario, Unspecified [Domain] Pro Forma Pro Forma [Member] New Accounting Pronouncements or Change in Accounting Principle [Line Items] New Accounting Pronouncements or Change in Accounting Principle [Line Items] Employee service share-based compensation, tax benefit Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount Schedule of Financing Receivable, Allowance for Credit Losses [Table] Schedule of Financing Receivable, Allowance for Credit Losses [Table] Changes in Allowance for Loan Losses Allowance for Loan and Lease Losses [Roll Forward] Balance, beginning of year Provision for loan losses Loans charged off Allowance for Loan and Lease Losses, Write-offs Recoveries of loans previously charged off Allowance for Loan and Lease Loss, Recovery of Bad Debts Balance, end of year Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative [Table] Derivative [Table] Hedging Relationship [Axis] Hedging Relationship [Axis] Hedging Relationship [Domain] Hedging Relationship [Domain] Cash flow hedges Cash Flow Hedging [Member] Fair value hedges Fair Value Hedging [Member] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract [Domain] Derivative Contract [Domain] Interest Rate Contract Interest Rate Contract [Member] Interest rate swaps Borrower Borrower [Member] Borrower [Member] Brokerage Activities Brokerage Activities [Member] Brokerage Activities [Member] Interest rate swap - risk participation agreement Interest Rate Swap, Risk Participation Agreement [Member] Interest Rate Swap, Risk Participation Agreement [Member] Interest Rate Swap, Risk Participation Agreement, Credit Enhancements Provided By Counterparty Interest Rate Swap, Risk Participation Agreement, Credit Enhancements Provided By Counterparty [Member] Interest Rate Swap, Risk Participation Agreement, Credit Enhancements Provided By Counterparty [Member] Interest Rate Swap, Risk Participation Agreement, Credit Enhancements Provided By The Bank Interest Rate Swap, Risk Participation Agreement, Credit Enhancements Provided By The Bank [Member] Interest Rate Swap, Risk Participation Agreement, Credit Enhancements Provided By The Bank [Member] Hedging Designation [Axis] Hedging Designation [Axis] Hedging Designation [Domain] Hedging Designation [Domain] Designated as Hedging Instrument Designated as Hedging Instrument [Member] Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Derivative [Line Items] Derivative [Line Items] Estimated gain (loss) to be reclassified to interest expense Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net Forecasted transactions period Maximum Length of Time Hedged in Interest Rate Cash Flow Hedge Number of derivative instruments Derivative, Number of Instruments Held Notional amount Derivative, Notional Amount Net reduction to interest expense Increase (Decrease) in Interest Payable, Net Number of counterparties Derivative, Number Of Counterparties Derivative, Number Of Counterparties Number of customers Number Of Customers Number Of Customers Counterparty participation level, percent Counterparty Participation Level, Percent Counterparty Participation Level, Percent Amount of collateral Collateral Already Posted, Aggregate Fair Value Fair value of net derivative, asset position Assets Needed for Immediate Settlement, Aggregate Fair Value Number of counterparties above threshold Derivative, Number Of Counterparties Above Minimum Collateral Posting Thresholds Derivative, Number of Counterparties above Minimum Collateral Posting Thresholds Fair value of net derivative Derivative, Net Liability Position, Aggregate Fair Value Cash and liquid assets Assets Designated To Deposits In Non Interest Earning Reserves Restricted Cash And Cash Equivalents Assets designated to deposits in non interest earning reserves restricted cash and cash equivalents. Common Stock Common Stock [Member] Additional Paid-in Capital Additional Paid-in Capital [Member] Unearned Compensation - ESOP Deferred Compensation, Share-based Payments [Member] Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock [Member] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance (in shares) Balance Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Issuance of common stock for the acquisition of United Financial Bancorp, Inc (in shares) Stock Issued During Period, Shares, Acquisitions Issuance of common stock for the acquisition of United Financial Bancorp, Inc Stock Issued During Period, Value, Acquisitions Cancellation of treasury shares (in shares) Treasury Stock, Shares, Retired Cancellation of treasury shares Treasury Stock, Retired, Cost Method, Amount Common stock repurchased (in shares) Stock Repurchased During Period, Shares Common stock repurchased Stock Repurchased During Period, Value Share-based compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition ESOP shares released or committed to be released Amortization of ESOP Award Shares issued for stock options exercised (in shares) Shares issued for stock options exercised Stock Issued During Period, Value, Stock Options Exercised Shares issued for restricted stock grants (in shares) Stock Issued During Period, Shares, Restricted Stock Award, Gross Shares issued for restricted stock grants Stock Issued During Period, Value, Restricted Stock Award, Gross Cancellation of shares for tax withholding (in shares) Shares Paid for Tax Withholding for Share Based Compensation Cancellation of shares for tax withholding Adjustments Related to Tax Withholding for Share-based Compensation Forfeited unvested restricted stock (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Forfeited unvested restricted stock Stock Issued During Period, Value, Restricted Stock Award, Forfeitures Tax effects of share-based awards Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net Dividends declared ($0.40, $0.46, and $0.48 per common share) Dividends, Common Stock, Cash Balance (in shares) Balance OTHER COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] FAIR VALUE MEASUREMENT Fair Value Disclosures [Text Block] Derivative Instruments in Hedges, at Fair Value, Net [Abstract] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Fair Values Derivatives, Balance Sheet Location, by Derivative Contract Type [Table] Forward loan sale commitments Forward Loan Sale Commitments [Member] Forward Loan Sale Commitments [Member] Derivative loan commitments Derivative Loan Commitments [Member] Derivative Loan Commitments [Member] Interest Rate Swap Type [Axis] Interest Rate Swap Type [Axis] Interest Rate Swap Type [Axis] Interest Rate Swap Type [Domain] Interest Rate Swap Type [Domain] [Domain] for Interest Rate Swap Type [Axis] With Customers With Customers [Member] With Customers [Member] With Counterparties With Counterparties [Member] With Counterparties [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Other Assets Other Assets [Member] Other Liabilities Other Liabilities [Member] Derivatives, Fair Value [Line Items] Derivatives, Fair Value [Line Items] Derivative Assets Derivative Asset, Fair Value, Gross Asset Derivative Liabilities Derivative Liability, Fair Value, Gross Liability Interest and dividend income Interest expense on subordinated debentures Non-interest income Other non-interest expense Provision for income taxes Earnings per share: Stock Price (per share): Stock Price Per Share [Abstract] Stock Price Per Share [Abstract] High (usd per share) Stock Price Per Share High Stock price per share high. Low (usd per share) Stock Price Per Share Low Stock price per share low. MERGER Business Combination Disclosure [Text Block] Schedule of Financing Receivables Past Due [Table] Schedule of Financing Receivables Past Due [Table] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Axis] Financing Receivables, Period Past Due [Domain] Financing Receivables, Period Past Due [Domain] 30-59 Days Past Due Financing Receivables, 30 to 59 Days Past Due [Member] 60-89 Days Past Due Financing Receivables, 60 to 89 Days Past Due [Member] Past Due 90 Days or More Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Financing Receivable, Recorded Investment, Past Due [Line Items] Financing Receivable, Recorded Investment, Past Due [Line Items] Owner-occupied CRE Mortgage Loans on Real Estate [Abstract] Total Past Due Financing Receivable, Recorded Investment, Past Due Past Due 90 Days or More and Still Accruing Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing Loans on Non-accrual Net income Adjusted weighted-average common shares outstanding (in shares) Weighted Average Number of Shares Issued, Basic Less: average number of unvested ESOP award shares (in shares) Weighted Average Number of Shares, Employee Stock Ownership Plan Shares Not Committed to be Released Weighted-average basic shares outstanding (in shares) Dilutive effect of stock options (in shares) Dilutive Effect Of Stock Options Dilutive effect of stock options. Weighted-average diluted shares (in shares) Number of Contracts Financing Receivable, Modifications, Subsequent Default, Number of Contracts Recorded Investment Financing Receivable, Modifications, Subsequent Default, Recorded Investment DERIVATIVES AND HEDGING ACTIVITIES Derivative Instruments and Hedging Activities Disclosure [Text Block] NET INCOME PER SHARE Earnings Per Share [Text Block] Loan Restructuring Modification [Axis] Loan Restructuring Modification [Axis] Loan Restructuring Modification [Domain] Loan Restructuring Modification [Domain] Extended Maturity Extended Maturity [Member] Adjusted Interest Rates Contractual Interest Rate Reduction [Member] Adjusted Rate and Maturity Contractual Interest Rate Reduction And Extended Maturity [Member] Contractual Interest Rate Reduction And Extended Maturity [Member] Payment Deferral Payment Deferral [Member] Other Other Loan Restructuring Modifications [Member] Other Loan Restructuring Modifications [Member] Schedule of Federal Home Loan Bank Advances, by Branch of FHLB Bank [Table] Schedule of Federal Home Loan Bank Advances, by Branch of FHLB Bank [Table] Weighted Average Weighted Average [Member] Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items] Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items] Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract] Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract] 2016 Federal Home Loan Bank, Advances, Maturities Summary, Due in Remainder of Fiscal Year 2017 Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months 2018 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Two 2019 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Three 2020 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Four 2021 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Five Thereafter Federal Home Loan Bank, Advances, Maturities Summary, Due after Year Five Total federal home loan bank advances Federal Home Loan Bank Advances And Other Borrowings Federal Home Loan Bank Advances And Other Borrowings Weighted-Average rate in 2016 Federal Home Loan Bank Advances Branch Of Fhlb Bank Weighted Average Interest Rate Due In Remainder Of Fiscal Year Federal home loan bank advances branch of FHLB bank weighted average interest rate due in remainder of fiscal year. Weighted-Average rate in 2017 Federal Home Loan Bank Advances Branch Of Fhlb Bank Weighted Average Interest Rate Within One Year Federal home loan bank advances branch of FHLB bank weighted average interest rate due within one Year Weighted-Average rate in 2018 Federal Home Loan Bank Advances Branch Of Fhlb Bank Weighted Average Interest Rate Due From One To Two Years Federal home loan bank advances branch of FHLB bank weighted average interest rate due from one to two years. Weighted-Average rate in 2019 Federal Home Loan Bank Advances Branch Of Fhlb Bank Weighted Average Interest Rate Due From Two To Three Years Federal home loan bank advances branch of FHLB bank weighted average interest rate due from two to three years. Weighted-Average rate in 2020 Federal Home Loan Bank Advances Branch Of Fhlb Bank Weighted Average Interest Rate Due From Three To Four Years Federal home loan bank advances branch of FHLB bank weighted average interest rate due from three to four years. Weighted-Average rate in 2021 Federal Home Loan Bank Advances Branch Of FHLB Bank Weighted Average Interest Rate Due From Four To Five Years Federal Home Loan Bank Advances Branch Of FHLB Bank Weighted Average Interest Rate Due From Four To Five Years Weighted-Average rate Thereafter Federal Home Loan Bank Advances Branch Of Fhlb Bank Weighted Average Interest Rate Due After Five Years Federal home loan bank advances branch of FHLB bank weighted average interest rate due after five years. FHLBB, advances, branch of FHLB bank, interest rate Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate Other Commitments [Table] Other Commitments [Table] Other Commitments [Axis] Other Commitments [Axis] Other Commitments [Domain] Other Commitments [Domain] Tax credit partnerships Investment, Tax Credit Partnership Associated With Alternative Energy [Member] Investment, Tax Credit Partnership Associated With Alternative Energy [Member] Other Commitments [Line Items] Other Commitments [Line Items] Net carrying balance of investments Other Commitment Capital contribution commitments Contractual Obligation Quarterly Financial Information of Company Quarterly Financial Information [Table Text Block] ASSETS Cash and cash equivalents: Cash and Cash Equivalents, at Carrying Value [Abstract] Short-term investments Short-term Investments Total cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Available for sale securities-at fair value Held to maturity securities-at amortized cost Held-to-maturity Securities Loans held for sale Loans Receivable Held-for-sale, Net, Not Part of Disposal Group Loans receivable (net of allowance for loan losses of $42,798 in 2016 and $33,887 in 2015) Federal Home Loan Bank stock, at cost Accrued interest receivable Interest Receivable Deferred tax asset-net Premises and equipment-net Property, Plant and Equipment, Net Goodwill Goodwill Core deposit intangible Finite-Lived Core Deposits, Gross Cash surrender value of bank-owned life insurance Bank Owned Life Insurance LIABILITIES AND STOCKHOLDERS’ EQUITY Liabilities: Liabilities [Abstract] Deposits: Deposits [Abstract] Non-interest-bearing Noninterest-bearing Deposit Liabilities Interest-bearing Interest-bearing Deposit Liabilities Mortgagors’ and investors’ escrow accounts Mortgagors And Investors Escrow Accounts Mortgagor's and investors' escrow accounts. Advances from the Federal Home Loan Bank Advances from Federal Home Loan Banks Total liabilities Liabilities Commitments and contingencies (notes 7 and 20) Commitments and Contingencies Stockholders’ equity: Stockholders' Equity Attributable to Parent [Abstract] Preferred stock (no par value; 2,000,000 shares authorized; no shares issued) Preferred Stock, Value, Issued Common stock (no par value; 120,000,000 shares authorized; 50,786,671 and 49,941,428 shares issued and outstanding at December 31, 2016 and 2015, respectively) Common Stock, Value, Issued Additional paid-in capital Additional Paid in Capital, Common Stock Unearned compensation — ESOP Unearned ESOP Shares Retained earnings Retained Earnings (Accumulated Deficit) Accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive Income (Loss), Net of Tax Total stockholders’ equity Changes in Loans Outstanding, Related Parties Loans and Leases Receivable, Related Parties [Roll Forward] Balance, beginning of year Loans and Leases Receivable, Related Parties Loans related to parties who terminated service during the year Loans And Leases Receivable Related Parties Loan To Parties Terminated From Service Loans and leases receivable related parties loan to parties terminated from service. Additional loans and advances Loans and Leases Receivable, Related Parties, Additions Repayments Loans and Leases Receivable, Related Parties, Proceeds Balance, end of year Fair Value Inputs, Assets, Quantitative Information [Table] Fair Value Inputs, Assets, Quantitative Information [Table] Mortgage loans Mortgage Loans [Member]