Entity Central Index Key Collateral dependent impaired loans fair value. Real estate acquired through foreclosure fair value. Merger and integration cost. Segment other noninterest expense. Income (loss) before income taxes and elimination of intersegment profit. Elimination of intersegment profit. Customer service fees. Gain on loan origination and sale activities net excluding intercompany profit. Mortgage servicing revenue expense. Segment other noninterest income. Noninterest income excluding intercompany profit. Document and entity information. Document And Entity Information [Abstract] Document Type Document Type Amendment Flag Amendment Flag Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Trading Symbol Trading Symbol Entity Registrant Name Entity Registrant Name Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Current Reporting Status Entity Current Reporting Status Entity Small Business Entity Small Business Entity Emerging Growth Company Entity Emerging Growth Company Entity Ex Transition Period Entity Ex Transition Period Entity Common Stock, Shares Outstanding Entity Common Stock Shares Outstanding Entity Shell Company Entity Shell Company Entity File Number Entity File Number Entity Tax Identification Number Entity Tax Identification Number Entity Address, Address Line One Entity Address Address Line1 Entity Address, City or Town Entity Address City Or Town Entity Address, State or Province Entity Address State Or Province Entity Address, Postal Zip Code Entity Address Postal Zip Code City Area Code City Area Code Local Phone Number Local Phone Number Mortgage servicing rights. Mortgagors escrow accounts. Statement Of Financial Position [Abstract] Assets Assets [Abstract] Cash and due from banks Cash And Due From Banks Interest-bearing deposits Interest Bearing Deposits In Banks Total cash and cash equivalents Cash And Cash Equivalents At Carrying Value Certificates of deposit Certificates Of Deposit At Carrying Value Securities available for sale, at fair value Available For Sale Securities Loans held for sale, at fair value Loans Receivable Held For Sale Net Not Part Of Disposal Group Loans, net of allowance for loan losses of $4,154 in 2019 and $4,437 in 2018 Loans And Leases Receivable Net Reported Amount Federal Home Loan Bank of Boston stock, at cost Federal Home Loan Bank Stock Accrued interest receivable Accrued Investment Income Receivable Mortgage servicing rights, net Mortgage Servicing Rights Premises and equipment, net Property Plant And Equipment Net Bank-owned life insurance Bank Owned Life Insurance Foreclosed real estate, net Real Estate Acquired Through Foreclosure Other assets Other Assets Total assets Assets Liabilities and Stockholders' Equity Liabilities And Stockholders Equity [Abstract] Deposits: Deposits [Abstract] Non-interest bearing Noninterest Bearing Deposit Liabilities Interest bearing Interest Bearing Deposit Liabilities Brokered Interest Bearing Domestic Deposit Brokered Total deposits Deposits Federal Home Loan Bank of Boston advances Advances From Federal Home Loan Banks Mortgagors' escrow accounts Mortgagors Escrow Accounts Post-employment benefit obligations Postemployment Benefits Liability Noncurrent Other liabilities Other Liabilities Noncurrent Total liabilities Liabilities Commitments and contingencies (Note 14) Commitments And Contingencies Stockholders' Equity: Stockholders Equity [Abstract] Preferred stock, no par value; authorized: 1,000,000 shares; issued: none Preferred Stock Value Common stock, $.01 par value; authorized: 15,000,000 shares; issued and outstanding: 5,797,705 shares at June 30, 2019 and 5,903,793 shares at December 31, 2018 Common Stock Value Additional paid-in capital Additional Paid In Capital Common Stock Retained earnings Retained Earnings Accumulated Deficit ESOP-Unearned compensation Unearned E S O P Shares Accumulated other comprehensive loss, net of tax Accumulated Other Comprehensive Income Loss Net Of Tax Total stockholders' equity Stockholders Equity Total liabilities and stockholders' equity Liabilities And Stockholders Equity Loans, allowance for loan losses Loans And Leases Receivable Allowance Preferred stock, par value Preferred Stock No Par Value Preferred stock, shares authorized Preferred Stock Shares Authorized Preferred stock, shares issued Preferred Stock Shares Issued Common stock, par value Common Stock Par Or Stated Value Per Share Common stock, shares authorized Common Stock Shares Authorized Common stock, shares issued Common Stock Shares Issued Common stock, shares outstanding Common Stock Shares Outstanding Gain on loan origination and sale activities, net. Income Statement [Abstract] Interest and dividend income: Interest And Dividend Income Operating [Abstract] Loans Interest And Fee Income Loans And Leases Securities-taxable Dividend Income Securities Operating Taxable Securities-tax exempt Dividend Income Securities Operating Tax Exempt Interest-bearing deposits and certificates of deposit Interest Income And Fees Bankers Acceptances Certificates Of Deposit And Commercial Paper Total interest and dividend income Interest And Dividend Income Operating Interest expense: Interest Expense [Abstract] Deposits Interest Expense Deposits Federal Home Loan Bank of Boston advances Interest Expense Federal Home Loan Bank And Federal Reserve Bank Advances Long Term Total interest expense Interest Expense Net interest income Interest Income Expense Net Provision (credit) for loan losses Provision For Loan And Lease Losses Net interest income after provision (credit) for loan losses Interest Income Expense After Provision For Loan Loss Non-interest income: Noninterest Income [Abstract] Customer service fees Customer Service Fees Gain on loan origination and sale activities, net Gain On Loan Origination And Sale Activities Net Mortgage servicing fees, net Mortgage Servicing Revenue Expense Gain on sales of securities Debt And Equity Securities Gain Loss Increase in cash surrender value of life insurance Life Insurance Corporate Or Bank Owned Change In Value Other Noninterest Income Other Operating Income Total non-interest income Noninterest Income Non-interest expenses: Noninterest Expense [Abstract] Salaries and employee benefits Labor And Related Expense Occupancy and equipment Occupancy Net Data processing Communications And Information Technology Professional fees Professional Fees Marketing Marketing Expense Other Other Noninterest Expense Total non-interest expenses Noninterest Expense Income (loss) before income taxes Income Loss From Continuing Operations Before Income Taxes Extraordinary Items Noncontrolling Interest Income tax expense Income Tax Expense Benefit Net income (loss) Net Income Loss Weighted average common shares outstanding (basic and diluted) Weighted Average Number Of Share Outstanding Basic And Diluted Net income (loss) per common share (basic and diluted) Earnings Per Share Basic And Diluted Statement Of Income And Comprehensive Income [Abstract] Statement [Table] Statement [Table] Retirement Plan Type Retirement Plan Type [Axis] Retirement Plan Type Retirement Plan Type [Domain] Supplemental Retirement Plan [Member] Supplemental Employee Retirement Plan Defined Benefit [Member] Statement [Line Items] Statement [Line Items] Net income (loss) Securities available for sale: Other Comprehensive Income Available For Sale Securities Adjustment Net Of Tax Period Increase Decrease [Abstract] Unrealized holding gains (losses) Other Comprehensive Income Unrealized Holding Gain Loss On Securities Arising During Period Before Tax Reclassification adjustment for net gains realized in income Other Comprehensive Income Loss Reclassification Adjustment From A O C I For Sale Of Securities Before Tax Net unrealized gains (losses) Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Tax Related tax effects Other Comprehensive Income Loss Available For Sale Securities Tax Net-of-tax amount Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax Actuarial losses Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Net Unamortized Gain Loss Arising During Period Before Tax Prior service credits Other Comprehensive Income Loss Amortization Adjustment From A O C I Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Before Tax Net change in supplemental retirement plan Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Before Tax Related tax effects Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Tax Net-of-tax amount Other Comprehensive Income Loss Pension And Other Postretirement Benefit Plans Adjustment Net Of Tax Total other comprehensive income (loss) Other Comprehensive Income Loss Net Of Tax Comprehensive income (loss) Comprehensive Income Net Of Tax Employee stock ownership plan ESOP shares committed to be released value. Statement Of Stockholders Equity [Abstract] Equity Components Statement Equity Components [Axis] Equity Component Equity Component [Domain] Common Stock [Member] Common Stock [Member] Additional Paid-in Capital [Member] Additional Paid In Capital [Member] Retained Earnings [Member] Retained Earnings [Member] Unearned compensation ESOP. Unearned Compensation ESOP [Member] Unearned Compensation E S O P [Member] Accumulated Other Comprehensive Loss [Member] Accumulated Other Comprehensive Income [Member] Beginning balance Beginning balance, shares Shares Outstanding Other comprehensive income (loss) Stock repurchased Stock Repurchased During Period Value Stock repurchased, shares Stock Repurchased During Period Shares Restricted stock awards granted Stock Issued During Period Value Restricted Stock Award Gross Restricted stock awards granted, shares Stock Issued During Period Shares Restricted Stock Award Gross Stock-based compensation Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value Restricted stock awards forfeited Stock Issued During Period Value Restricted Stock Award Forfeitures Restricted stock awards forfeited, shares Stock Issued During Period Shares Share Based Compensation Forfeited ESOP shares committed to be released Employee Stock Ownership Plan E S O P Shares Committed To Be Released Value Ending balance Ending balance, shares Increase decrease in mortgage servicing rights. Payments for proceeds from acquiring certificate of deposit. Proceeds from pay downs of mortgage backed securities available for sale. Net increase in non-brokered deposits. Net increase (decrease) in brokered deposits. Increase (decrease) in long term loans to federal home loan banks. Increase (decrease) in mortgagors' escrow accounts, net. Interest paid on deposits and borrowed funds. Statement Of Cash Flows [Abstract] Cash flows from operating activities: Net Cash Provided By Used In Operating Activities [Abstract] Net income (loss) Profit Loss Adjustments to reconcile net income (loss) to net cash used in operating activities: Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract] Loans originated for sale Payments For Origination Of Mortgage Loans Held For Sale Net gain on sales of mortgage loans Gain Loss On Sale Of Mortgage Loans Proceeds from sales of mortgage loans Proceeds From Sale Of Mortgage Loans Held For Sale Net amortization of securities Accretion Amortization Of Discounts And Premiums Investments Net change in deferred loan costs and fees, and purchase premiums Increase Decrease In Loans Deferred Income Gain on sales of securities Depreciation and amortization Depreciation Amortization And Accretion Net Stock-based compensation Share Based Compensation ESOP expense Employee Stock Ownership Plan E S O P Compensation Expense Increase in cash surrender value of life insurance Increase Decrease In Life Insurance Liabilities Net increase in mortgage servicing rights Increase Decrease In Mortgage Servicing Rights Other, net Other Operating Activities Cash Flow Statement Net cash used in operating activities Net Cash Provided By Used In Operating Activities Cash flows from investing activities: Net Cash Provided By Used In Investing Activities [Abstract] Redemptions of certificates of deposit Payments For Proceeds From Acquiring Certificate Of Deposit Securities available for sale: Payments For Proceeds From Investments [Abstract] Calls/maturities Proceeds From Maturities Prepayments And Calls Of Available For Sale Securities Purchases Payments To Acquire Available For Sale Securities Sales Proceeds From Sale Of Available For Sale Securities Principal payments on mortgage-backed securities Proceeds From Pay Downs Of Mortgage Backed Securities Available For Sale Loan originations, net of principal repayments Payments For Proceeds From Loans And Leases Loan purchases Payments To Acquire Loans Receivable Proceeds from residential portfolio loan sale Proceeds From Sale Of Loans And Leases Held For Investment (Purchases) redemptions of Federal Home Loan Bank of Boston stock Payments For Proceeds From Federal Home Loan Bank Stock Purchases of premises and equipment Payments To Acquire Property Plant And Equipment Net cash provided by (used in) investing activities Net Cash Provided By Used In Investing Activities Cash flows from financing activities: Net Cash Provided By Used In Financing Activities [Abstract] Net increase in non-brokered deposits Net Increase In Non Brokered Deposits Net increase in brokered deposits Net Increase Decrease In Brokered Deposits Net increase (decrease) in short-term Federal Home Loan Bank of Boston borrowings Increase Decrease In Loans To Federal Home Loan Banks Issuance of long-term Federal Home Loan Bank of Boston advances Increase Decrease In Long Term Loans To Federal Home Loan Banks Repayments of long-term Federal Home Loan Bank of Boston advances Repayments Of Federal Home Loan Bank Borrowings Net increase (decrease) in mortgagors' escrow accounts Increase Decrease In Mortgagors Escrow Accounts Net Repurchases of common stock Payments For Repurchase Of Common Stock Net cash provided by financing activities Net Cash Provided By Used In Financing Activities Net change in cash and cash equivalents Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect Cash and cash equivalents at beginning of period Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Including Disposal Group And Discontinued Operations Cash and cash equivalents at end of period Supplemental cash flow information: Supplemental Cash Flow Information [Abstract] Interest paid on deposits and borrowed funds Interest Paid On Deposits And Borrowed Funds Income taxes paid Income Taxes Paid Net Non-cash items: Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract] Transfer of held for sale loans to portfolio Transfer Of Loans Held For Sale To Portfolio Loans1 Transfer of portfolio loans to held for sale Transfer Of Portfolio Loans And Leases To Held For Sale1 Organization Consolidation And Presentation Of Financial Statements [Abstract] Basis of Financial Statement Presentation Organization Consolidation And Presentation Of Financial Statements Disclosure [Text Block] Accounting Changes And Error Corrections [Abstract] Recent Accounting Pronouncements New Accounting Pronouncements And Changes In Accounting Principles [Text Block] Equity [Abstract] Accumulated Other Comprehensive Loss Comprehensive Income Note [Text Block] Investments, Debt and Equity Securities [Abstract] Securities Available for Sale Investments In Debt And Marketable Equity Securities And Certain Trading Assets Disclosure [Text Block] Receivables [Abstract] Loans and Allowance for Loan Losses Loans Notes Trade And Other Receivables Disclosure [Text Block] Transfers And Servicing [Abstract] Loan Servicing Transfers And Servicing Of Financial Assets [Text Block] Income Tax Disclosure [Abstract] Income Taxes Income Tax Disclosure [Text Block] Derivative Instruments And Hedging Activities Disclosure [Abstract] On-Balance Sheet Derivative Instruments and Hedging Activities Derivative Instruments And Hedging Activities Disclosure [Text Block] Disclosure Of Compensation Related Costs Sharebased Payments [Abstract] Employee Stock Ownership Plan Disclosure Of Compensation Related Costs Share Based Payments [Text Block] Share Repurchase Program Stockholders Equity Note Disclosure [Text Block] Earnings Per Share [Abstract] Earnings (Loss) Per Share Earnings Per Share [Text Block] Stock-Based Compensation Shareholders Equity And Share Based Payments [Text Block] Fair Value Disclosures [Abstract] Fair Value of Assets and Liabilities Fair Value Disclosures [Text Block] Commitments And Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments And Contingencies Disclosure [Text Block] Segment Reporting [Abstract] Segment Information Segment Reporting Disclosure [Text Block] Revenue From Contract With Customer [Abstract] Revenue from Contracts with Customers Revenue From Contract With Customer [Text Block] Accounting Policies [Abstract] Recent Accounting Pronouncements New Accounting Pronouncements Policy Policy [Text Block] Components of Accumulated Other Comprehensive Loss and Related Tax Effects Schedule Of Comprehensive Income Loss Table [Text Block] Schedule of amortized cost and fair value of securities Available For Sale Securities [Text Block] Investments Classified by Contractual Maturity Date Investments Classified By Contractual Maturity Date Table [Text Block] Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Available For Sale Securities Continuous Unrealized Loss Position Fair Value Table [Text Block] Summary of Loan Portfolio Schedule Of Accounts Notes Loans And Financing Receivable [Text Block] Summary of Activity in the Allowance for Loan Losses by Loan Category Schedule Of Credit Losses Related To Financing Receivables Current And Noncurrent Table [Text Block] Summary of Additional Information Pertaining to the Allowance for Loan Losses Allowance For Credit Losses On Financing Receivables Table [Text Block] Schedule of Past Due and Non-Accrual Loans Past Due Financing Receivables Table [Text Block] Summary of Impaired Loans and Additional Information Pertaining to Impaired Loans Impaired Financing Receivables Table [Text Block] Summary of Company's Loans by Risk Rating Financing Receivable Credit Quality Indicators Table [Text Block] Summary of Activity Relating to Mortgage Servicing Rights Schedule Of Servicing Assets At Fair Value [Text Block] Schedule of Calculation of Average Number of Shares Outstanding Used to Calculate Basic and Diluted Income (Loss) Per Share Schedule Of Weighted Average Number Of Shares Table [Text Block] Summary of Grants of Options to Purchase Shares of Common Stock Schedule Of Share Based Payment Award Stock Options Valuation Assumptions Table [Text Block] Summary of Stock Options Activity Schedule Of Share Based Compensation Stock Options Activity Table [Text Block] Summary of Activity in Restricted Stock Awards Under Equity Plan Schedule Of Sharebased Compensation Restricted Stock And Restricted Stock Units Activity Table [Text Block] Schedule of Assets and Liabilities Recorded at Fair Value on a Recurring Basis Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis Table [Text Block] Schedule of Assets Recorded at Fair Value on a Non-Recurring Basis Fair Value Assets Measured On Nonrecurring Basis [Text Block] Summary of Carrying Values, Estimated Fair Values and Placement in Fair Value Hierarchy of Company's Financial Instruments Fair Value By Balance Sheet Grouping [Text Block] Summary of Financial Instruments Outstanding Contract Amounts Represent Credit Risk Schedule Of Fair Value Off Balance Sheet Risks [Text Block] Summary of Segment Information Schedule Of Segment Reporting Information By Segment [Text Block] Accumulated Other Comprehensive Income Loss [Table] Accumulated Other Comprehensive Income Loss [Table] Accumulated Net Investment Gain (Loss) Attributable to Parent Accumulated Net Unrealized Investment Gain Loss [Member] Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment Net Unamortized Gain Loss [Member] Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment Net Prior Service Cost Credit [Member] Accumulated Defined Benefit Plans Adjustment Attributable to Parent [Member] Accumulated Defined Benefit Plans Adjustment [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income Loss [Line Items] Net unrealized gain (loss) Other Comprehensive Income Loss Before Tax Other comprehensive Loss, Tax effect Other Comprehensive Income Loss Tax Investments Debt And Equity Securities [Abstract] Schedule Of Available For Sale Securities [Table] Schedule Of Available For Sale Securities [Table] Financial Instrument Financial Instrument [Axis] Financial Instruments Transfers And Servicing Of Financial Instruments Types Of Financial Instruments [Domain] Debt Securities [Member] Debt Securities [Member] Equity Securities [Member] Equity Securities [Member] Investment Type Investment Type [Axis] Investments Investment Type Categorization [Member] US Government-sponsored Enterprises [Member] U S Government Sponsored Enterprises Debt Securities [Member] Corporate [Member] Corporate Debt Securities [Member] Municipal [Member] Municipal Bonds [Member] Residential Mortgage-backed Securities, US Government Sponsored Enterprises [Member] Mortgage Backed Securities Issued By U S Government Sponsored Enterprises [Member] Commercial mortgage backed securities issued by US government sponsored enterprises. Commercial Mortgage-backed Securities, US Government Sponsored Enterprises [Member] Commercial Mortgage Backed Securities Issued By U S Government Sponsored Enterprises [Member] Commercial Mortgage Backed Securities, U.S. Government-guaranteed [Member] Commercial Mortgage Backed Securities [Member] Collateralized mortgage obligations issued by US government sponsored enterprises. Collateralized Mortgage Obligations, US Government Sponsored Enterprises [Member] Collateralized Mortgage Obligations Issued By U S Government Sponsored Enterprises [Member] Collateralized mortgage obligations issued by US government guaranteed. Collateralized Mortgage Obligations, US Government Guaranteed [Member] Collateralized Mortgage Obligations Issued By U S Government Guaranteed [Member] Schedule of Available-for-sale Securities [Line Items] Schedule Of Available For Sale Securities [Line Items] Amortized Cost Available For Sale Securities Amortized Cost Gross Unrealized Gains Available For Sale Securities Accumulated Gross Unrealized Gain Before Tax Gross Unrealized Losses Available For Sale Securities Accumulated Gross Unrealized Loss Before Tax Fair Value Proceeds from sales of available-for-sale securities Available-for-sale securities, gross realized gains Available For Sale Securities Gross Realized Gains Available-for-sale securities, gross realized losses Available For Sale Securities Gross Realized Losses Available-for-sale Securities, Debt Maturities, Amortized Cost Available For Sale Securities Debt Maturities Amortized Cost [Abstract] Within 1 year Available For Sale Securities Debt Maturities Within One Year Amortized Cost After 1 year through 5 years Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost After 5 years through 10 years Available For Sale Securities Debt Maturities After Five Through Ten Years Amortized Cost Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Total Available For Sale Securities Debt Maturities Single Maturity Date Amortized Cost Basis Mortgage-backed securities Available For Sale Securities Debt Maturities Without Single Maturity Date Amortized Cost Available-for-sale Debt Securities, Amortized Cost Basis, Total Available For Sale Debt Securities Amortized Cost Basis Available-for-sale Securities, Debt Maturities, Fair Value Available For Sale Securities Debt Maturities Fair Value [Abstract] Within 1 year Available For Sale Securities Debt Maturities Within One Year Fair Value After 1 year through 5 years Available For Sale Securities Debt Maturities After One Through Five Years Fair Value After 5 years through 10 years Available For Sale Securities Debt Maturities After Five Through Ten Years Fair Value Available-for-sale Securities, Debt Maturities, Single Maturity Date, Fair Value Total Available For Sale Securities Debt Maturities Single Maturity Date Mortgage-backed securities Available For Sale Securities Debt Maturities Without Single Maturity Date Fair Value Available-for-sale Securities, Debt Securities, Fair Value Total Available For Sale Securities Debt Securities Less Than Twelve Months, Gross Unrealized Losses Available For Sale Securities Continuous Unrealized Loss Position Less Than12 Months Accumulated Loss Less Than Twelve Months, Fair Value Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value Over Twelve Months, Gross Unrealized Losses Available For Sale Securities Continuous Unrealized Loss Position12 Months Or Longer Accumulated Loss Over Twelve Months, Fair Value Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value Number of debt securities with unrealized losses. Unrealized losses debt securities aggregate depreciation percentage. Number of debt securities with unrealized losses Number Of Debt Securities With Unrealized Losses Unrealized losses debt securities aggregate depreciation percentage Unrealized Losses Debt Securities Aggregate Depreciation Percentage Accounts Notes Loans And Financing Receivable [Abstract] Accounts Notes Loans And Financing Receivable [Abstract] Schedule Of Accounts Notes Loans And Financing Receivable [Table] Schedule Of Accounts Notes Loans And Financing Receivable [Table] Class of Financing Receivable, Type Financing Receivable Recorded Investment By Class Of Financing Receivable [Axis] Class of Financing Receivable, Type Financing Receivable Recorded Investment Class Of Financing Receivable [Domain] 1-4 family. One-to-Four Family [Member] One To Four Family Loans [Member] Home equity loans and lines of credit. Home Equity Loans and Lines of Credit [Member] Home Equity Loans And Lines Of Credit [Member] Construction [Member] Construction Loans [Member] Financing Receivable Portfolio Segment Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment Financing Receivable Portfolio Segment [Domain] Residential Real Estate [Member] Residential Portfolio Segment [Member] Commercial Real Estate Loans [Member] Commercial Real Estate Portfolio Segment [Member] Commercial and industrial. Commercial and Industrial [Member] Commercial And Industrial Portfolio Segment [Member] Consumer [Member] Consumer Portfolio Segment [Member] Industry Sector Equity Securities By Industry [Axis] Industry Sector Equity Securities Industry [Member] Real Estate Sector [Member] Real Estate Sector [Member] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts Notes And Loans Receivable [Line Items] Total loans Loans And Leases Receivable Gross Carrying Amount Allowance for loan losses Net deferred loan costs and fees, and purchase premiums Loans And Leases Receivable Net Of Deferred Income Net loans Fair value adjustment included in gain on loan origination and sale activities. Residential Mortgage [Member] Residential Mortgage [Member] Subsequent Event Type Subsequent Event Type [Axis] Subsequent Event Type Subsequent Event Type [Domain] Subsequent Event [Member] Subsequent Event [Member] Range Range [Axis] Range Range [Member] Minimum [Member] Minimum [Member] Maximum [Member] Maximum [Member] Non accrual loans. Non Accrual Loans [Member] Non Accrual Loans [Member] Other modified loan. Other Modified Loan [Member] Other Modified Loan [Member] Financing Receivables, Period Past Due Financing Receivables Period Past Due [Axis] Financing Receivables, Period Past Due Financing Receivables Period Past Due [Domain] 30 - 59 Days Past Due [Member] Financing Receivables30 To59 Days Past Due [Member] Consumer Loans [Member] Consumer Loan [Member] Internal Credit Assessment Internal Credit Assessment [Axis] Internal Credit Assessment Internal Credit Assessment [Domain] Doubtful [Member] Doubtful [Member] Substandard [Member] Substandard [Member] Special Mention [Member] Special Mention [Member] Fair value adjustment included in gain on loan orgination and sale activities Fair Value Adjustment Included In Gain On Loan Origination And Sale Activities Transferred loans committed to sell Loans Receivable Held For Sale Amount Schedule Of Financing Receivable Allowance For Credit Losses [Table] Schedule Of Financing Receivable Allowance For Credit Losses [Table] Second mortgages and HELOC. Second Mortgages and HELOC [Member] Second Mortgages And Home Equity Loans And Lines Of Credit [Member] Financing Receivable, Allowance for Credit Losses [Line Items] Financing Receivable Allowance For Credit Losses [Line Items] Beginning balance Financing Receivable Allowance For Credit Losses Provision (credit) for loan losses Loans charged-off Financing Receivable Allowance For Credit Losses Write Offs Recoveries Financing Receivable Allowance For Credit Losses Recovery Ending balance Allowance for impaired loans Financing Receivable Allowance For Credit Losses Individually Evaluated For Impairment1 Allowance for non-impaired loans Financing Receivable Allowance For Credit Losses Collectively Evaluated For Impairment Total allowance for loan losses Impaired loans Financing Receivable Individually Evaluated For Impairment Non-impaired loans Financing Receivable Collectively Evaluated For Impairment Total loans Schedule Of Financing Receivables Past Due [Table] Schedule Of Financing Receivables Past Due [Table] 60 - 89 Days Past Due [Member] Financing Receivables60 To89 Days Past Due [Member] 90 Days or More Past Due [Member] Financing Receivables Equal To Greater Than90 Days Past Due [Member] Financing Receivable, Recorded Investment, Past Due [Line Items] Financing Receivable Recorded Investment Past Due [Line Items] Total Past Due Financing Receivable Recorded Investment Past Due Non-accrual Loans Financing Receivable Recorded Investment Nonaccrual Status Impaired financing receivable with no related allowance. Schedule Of Impaired Financing Receivable [Table] Schedule Of Impaired Financing Receivable [Table] Financing Receivable, Impaired [Line Items] Financing Receivable Impaired [Line Items] Recorded Investment without a valuation allowance Impaired Financing Receivable With No Related Allowance Recorded Investment Unpaid Principal Balance without a valuation allowance Impaired Financing Receivable With No Related Allowance Unpaid Principal Balance Related Allowance without a valuation allowance Impaired Financing Receivable With No Related Allowance Recorded Investment with a valuation allowance Impaired Financing Receivable With Related Allowance Recorded Investment Unpaid Principal Balance with a valuation allowance Impaired Financing Receivable With Related Allowance Unpaid Principal Balance Related Allowance, Total impaired loans Impaired Financing Receivable Related Allowance Recorded Investment, Total impaired loans Impaired Financing Receivable Recorded Investment Unpaid Principal Balance, Total impaired loans Impaired Financing Receivable Unpaid Principal Balance Loan And Lease Receivables Impaired [Abstract] Average Recorded Investment Impaired Financing Receivable Average Recorded Investment Interest Income Recognized Impaired Financing Receivable Interest Income Accrual Method Cash Basis Interest Recognized Impaired Financing Receivable Interest Income Cash Basis Method Impaired loans, additional funds committed Loans And Leases Receivable Impaired Commitment To Lend Troubled debt restructuring interest rate concession period. Troubled debt restructuring, interest rate concession period Troubled Debt Restructuring Interest Rate Concession Period Loans subject to troubled debt restructurings Financing Receivable Modifications Number Of Contracts2 Loans subject to troubled debt restructurings, amount Financing Receivable Modifications Recorded Investment Troubled debt restructuring amount Financing Receivable Modifications Post Modification Recorded Investment2 Changes to allowance for loan losses Allowance For Credit Losses Change In Method Of Calculating Impairment Troubled debt restructurings defaulted over 30 days past due Financing Receivable Modifications Subsequent Default Recorded Investment1 Pass [Member] Pass [Member] Minimum past due days for loan rating. Minimum past due days for loan rating Minimum Past Due Days For Loan Rating Unpaid principal balance of residential mortgage loans serviced for others. Unpaid principal balances of residential mortgage loans serviced for others Unpaid Principal Balances Of Residential Mortgage Loans Serviced For Others Mortgage servicing rights, net. Mortgage servicing rights: Servicing Asset At Amortized Value Balance Roll Forward Balance at beginning of year Servicing Asset At Amortized Value Additions through originations Servicing Asset At Amortized Value Additions Amortization Servicing Asset At Amortized Value Amortization1 Balance at end of period Valuation allowance: Valuation Allowance For Impairment Of Recognized Servicing Assets Roll Forward Balance at beginning of year Valuation Allowance For Impairment Of Recognized Servicing Assets Balance Provision (credit) Valuation Allowance For Impairment Of Recognized Servicing Assets Provisions Recoveries Balance at end of period Amortized cost, net Mortgage Servicing Rights Net Fair value Servicing Asset At Fair Value Amount Increase (reduced) the valuation allowance of mortgage servicing rights Valuation Allowance For Impairment Of Recognized Servicing Assets Period Increase Decrease Current state tax expense Current State And Local Tax Expense Benefit Reversal of federal tax expense benefit Tax Adjustments Settlements And Unusual Provisions Net operating loss carryforward Deferred Tax Assets Operating Loss Carryforwards Valuation allowance on deferred tax assets Deferred Tax Assets Valuation Allowance Derivative [Table] Derivative [Table] Balance Sheet Location Balance Sheet Location [Axis] Balance Sheet Location Balance Sheet Location [Domain] Other Assets [Member] Other Assets [Member] Derivative loan commitments. Derivative Loan Commitments [Member] Derivative Loan Commitments [Member] Other Liabilities [Member] Other Liabilities [Member] Forward loan sale commitments and to be announced securities. Undesignated Forward Loan Sale Commitments and TBA Securities [Member] Forward Loan Sale Commitments And To Be Announced Securities [Member] Derivative [Line Items] Derivative [Line Items] Derivative, Notional amount Derivative Notional Amount Derivative fair value, Asset Derivative Assets Derivative fair value, Liability Derivative Liabilities Fair value of derivative instruments Derivative Instruments In Hedges At Fair Value Net Term of loan repaid by employee stock ownership plan. Schedule Of Employee Stock Ownership Plan E S O P Disclosures [Table] Schedule Of Employee Stock Ownership Plan E S O P Disclosures [Table] Related Party Related Party Transactions By Related Party [Axis] Related Party Related Party [Domain] The Randolph Savings Charitable Foundation, Inc. The Randolph Savings Charitable Foundation, Inc. [Member] Foundation [Member] Employee Stock Ownership Plan E S O P Disclosures [Line Items] Employee Stock Ownership Plan E S O P Disclosures [Line Items] Sale of share in employee stock ownership plan Stock Issued During Period Shares Employee Stock Ownership Plan Sale of stock, price per share Sale Of Stock Price Per Share Loan repaid term Term Of Loan Repaid By Employee Stock Ownership Plan Annual allocation of shares expiration year. Employee stock ownership plan number of unallocated shares. Employee stock ownership plan fair value of unallocated shares. Number of allocated shares Employee Stock Ownership Plan E S O P Number Of Allocated Shares Annual allocation of shares, expiration year Annual Allocation Of Shares Expiration Year Unallocated shares Employee Stock Ownership Plan Number Of Unallocated Shares Unallocated shares, value Employee Stock Ownership Plan Fair Value Of Unallocated Shares Stock repurchase program percentage of outstanding shares repurchased. Schedule Of Stock By Class [Table] Schedule Of Stock By Class [Table] Share Repurchase Program Share Repurchase Program [Axis] Share Repurchase Program Share Repurchase Program [Domain] September two thousand seventeen share repurchase program. September 2017 Share Repurchase Program [Member] September Two Thousand Seventeen Share Repurchase Program [Member] Class Of Stock [Line Items] Class Of Stock [Line Items] Stock repurchase program percentage of outstanding shares repurchased Stock Repurchase Program Percentage Of Outstanding Shares Repurchased Number of shares authorized to repurchase Stock Repurchase Program Number Of Shares Authorized To Be Repurchased Number of shares repurchased Cost of shares repurchased Potentially dilutive common stock equivalents outstanding Weighted Average Number Diluted Shares Outstanding Adjustment Average number of common shares outstanding Weighted Average Number Of Shares Outstanding Basic Less: Average unallocated ESOP shares Weighted Average Number Of Shares Employee Stock Ownership Plan Shares Not Committed To Be Released Average number of common shares outstanding (basic and diluted) Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table] Plan Name Plan Name [Axis] Plan Name Plan Name [Domain] Two thousand seventeen stock option and incentive plan. Two Thousand Seventeen Stock Option and Incentive Plan [Member] Two Thousand Seventeen Stock Option And Incentive Plan [Member] Award Type Award Type [Axis] Equity Award Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain] Stock Options [Member] Employee Stock Option [Member] Restricted Stock [Member] 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] Shares reserved for issuance Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized Stock options term Sharebased Compensation Arrangement By Sharebased Payment Award Expiration Period Options and awards vesting period Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period1 Options granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Gross Vesting period (years) Expiration period (years) Expected volatility Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Volatility Rate Expected life (years) Sharebased Compensation Arrangement By Sharebased Payment Award Fair Value Assumptions Expected Term1 Expected dividend yield Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Dividend Rate Risk free interest rate Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Risk free interest rate, minimum Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Minimum Risk free interest rate, maximum Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Risk Free Interest Rate Maximum Option fair value Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Grant Date Fair Value Stock Option Grants Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Granted Expired Share Based Compensation Arrangement By Share Based Payment Award Options Expirations In Period Ending Balance Exercisable at June 30, 2019 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Unrecognized compensation cost (inclusive of directors' options) Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Stock Options Weighted average remaining recognition period (years) Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Period For Recognition1 Weighted Average Exercise Price Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Rollforward Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Weighted Average Exercise Price Granted Share Based Compensation Arrangements By Share Based Payment Award Options Grants In Period Weighted Average Exercise Price Expired Share Based Compensation Arrangements By Share Based Payment Award Options Expirations In Period Weighted Average Exercise Price Ending Balance Exercisable at June 30, 2019 Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Weighted Average Exercise Price Share-based compensation arrangement by share-based payment award, options, grants in period, weighted average remaining contractual term. Share-based compensation arrangement by share-based payment award, options, forfeitures, weighted average remaining contractual term. Weighted Average Remaining Contractual Term Sharebased Compensation Arrangement By Sharebased Payment Award Options Outstanding Weighted Average Remaining Contractual Term2 Weighted Average Remaining Contractual Term, Granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Weighted Average Remaining Contractual Term Weighted Average Remaining Contractual Term, Expired Share Based Compensation Arrangement By Share Based Payment Award Options Forfeitures Weighted Average Remaining Contractual Term Share-based compensation arrangement by Share-based payment award options forfeited intrinsic value. Weighted Average Remaining Contractual Term and Aggregate Intrinsic Value Share Based Compensation Arrangement By Share Based Payment Award Options Additional Disclosures [Abstract] Aggregate Intrinsic Value, Outstanding Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Intrinsic Value Aggregate Intrinsic Value, Granted Share Based Compensation Arrangement By Share Based Payment Award Options Grants In Period Grant Date Intrinsic Value Aggregate Intrinsic Value, Expired Share Based Compensation Arrangement By Share Based Payment Award Options Forfeited Intrinsic Value Aggregate Intrinsic Value, Outstanding Aggregate Intrinsic Value, Exercisable Sharebased Compensation Arrangement By Sharebased Payment Award Options Exercisable Intrinsic Value1 Stock-based compensation expense Allocated Share Based Compensation Expense Restricted Stock Awards Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Roll Forward Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Number Granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Vested Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeited In Period Ending Balance Unrecognized compensation cost Employee Service Share Based Compensation Nonvested Awards Total Compensation Cost Not Yet Recognized Share Based Awards Other Than Options Weighted Average Grant Price Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Roll Forward Beginning Balance Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Nonvested Weighted Average Grant Date Fair Value Granted Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Grants In Period Weighted Average Grant Date Fair Value Vested Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Vested In Period Weighted Average Grant Date Fair Value Forfeited Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Other Than Options Forfeitures Weighted Average Grant Date Fair Value Ending Balance Portfolio loans fair value disclosure. Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table] Measurement Frequency Fair Value By Measurement Frequency [Axis] Fair Value, Measurement Frequency Fair Value Measurement Frequency [Domain] Fair Value, Measurements, Recurring [Member] Fair Value Measurements Recurring [Member] Fair Value Hierarchy and NAV Fair Value By Fair Value Hierarchy Level [Axis] Fair Value Hierarchy and NAV Fair Value Measurements Fair Value Hierarchy [Domain] Level 1 [Member] Fair Value Inputs Level1 [Member] Level 2 [Member] Fair Value Inputs Level2 [Member] Level 3 [Member] Fair Value Inputs Level3 [Member] Forward loan sale commitments. Forward Loan Sale Commitments [Member] Forward Loan Sale Commitments [Member] Forward loan sale commitments, including TBAs. Forward Loan Sale Commitments, including TBAs [Member] Forward Loan Sale Commitments Including T B As [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] Fair value, Portfolio loans Portfolio Loans Fair Value Disclosure Fair value, Loans held for sale Loans Held For Sale Fair Value Disclosure Derivative assets Derivative liabilities Fair Value, Measurements, Nonrecurring [Member] Fair Value Measurements Nonrecurring [Member] Fair value, assets, level 1 to level 2 transfers, amount Fair Value Assets Level1 To Level2 Transfers Amount Fair value, assets, level 2 to level 1 transfers, amount Fair Value Assets Level2 To Level1 Transfers Amount Fair value, liabilities, level 1 to level 2 transfers, amount Fair Value Liabilities Level1 To Level2 Transfers Amount Fair value, liabilities, level 2 to level 1 transfers, amount Fair Value Liabilities Level2 To Level1 Transfers Amount Gains losses on assets held. Gain loss on sale of collateral dependent impaired loans. Gains losses on assets held mortgage servicing rights. Gains losses on assets held foreclosed real estate. Fair value, Collateral dependent impaired loans Collateral Dependent Impaired Loans Fair Value Mortgage servicing rights, fair value Fair value, Foreclosed real estate Real Estate Acquired Through Foreclosure Fair Value Assets, Fair Value Disclosure Assets Fair Value Disclosure Gains (Losses) on collateral dependent impaired loans Gain Loss On Sale Of Collateral Dependent Impaired Loans Gains (losses) on assets held, mortgage servicing rights Gains Losses On Assets Held Mortgage Servicing Rights Gains (losses) on assets held, foreclosed real estate Gains Losses On Assets Held Foreclosed Real Estate Gains (Losses) on assets held Gains Losses On Assets Held Increase (decrease) in valuation allowance of mortgage servicing rights Liabilities measured at fair value on nonrecurring basis Liabilities Fair Value Disclosure Certificate of deposits fair value disclosure. Measurement Basis Fair Value By Measurement Basis [Axis] Fair Value Disclosure Item Amounts [Default] Portion At Fair Value Fair Value Disclosure [Member] Fair Value Measurement Fair Value Disclosure Item Amounts [Domain] Carrying Amount [Member] Carrying Reported Amount Fair Value Disclosure [Member] Fair Value [Member] Estimate Of Fair Value Fair Value Disclosure [Member] Financial assets: Financial Instruments Financial Assets Balance Sheet Groupings [Abstract] Certificates of deposit Certificate Of Deposits Fair Value Disclosure Securities available for sale Loans held for sale Loans, net Loans Receivable Fair Value Disclosure Financial liabilities: Financial Instruments Financial Liabilities Balance Sheet Groupings [Abstract] Deposits Deposits Fair Value Disclosure FHLBB advances Federal Home Loan Bank Borrowings Fair Value Disclosure Schedule Of Fair Value Off Balance Sheet Risks [Table] Schedule Of Fair Value Off Balance Sheet Risks [Table] Commitments to Originate Loans [Member] Loan Origination Commitments [Member] Unused lines and letters of credit. Unused Lines and Letters of Credit [Member] Unused Lines And Letters Of Credit [Member] Unadvanced funds on construction loans. Unadvanced Funds on Construction Loans [Member] Unadvanced Funds On Construction Loans [Member] Overdraft. Overdraft Lines of Credit [Member] Overdraft [Member] Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] Fair Value Off Balance Sheet Risks Disclosure Information [Line Items] Financial instruments with off-balance-sheet risk Fair Value Disclosure Offbalance Sheet Risks Face Amount Liability Number of branch offices. Schedule Of Segment Reporting Information By Segment [Table] Schedule Of Segment Reporting Information By Segment [Table] Segments Statement Business Segments [Axis] Segments Segment [Domain] Envision Mortgage. Envision Mortgage [Member] Envision Mortgage [Member] Envision Bank. Envision Bank [Member] Envision Bank [Member] Segment Reporting Information [Line Items] Segment Reporting Information [Line Items] Number of business segments Number Of Reportable Segments Number of branch offices Number Of Branch Offices Net interest income Gain on loan origination and sale activities, net Gain On Loan Origination And Sale Activities Net Excluding Intercompany Profit Other Segment Other Noninterest Income Total non-interest income Noninterest Income Excluding Intercompany Profit Merger and integration costs Merger And Integration Cost Other non-interest expenses Segment Other Noninterest Expense Income (loss) before income taxes and elimination of inter-segment profit Income Loss Before Income Taxes And Elimination Of Intersegment Profit Elimination of inter-segment profit Elimination Of Intersegment Profit Total assets Premium percentage for new loans. Percentage fees for HELOC origination. Premium percentage for new loans Premium Percentage For New Loans Premium income Premiums Earned Net Percentage of fees for HELOC Percentage Fees For H E L O C Origination Percentage of loan servicing fees. Percentage of loan servicing fees Percentage Of Loan Servicing Fees Servicing fees amount