Income Tax Disclosure [Abstract] Components of Deferred Tax Assets [Abstract] Allowance for loan losses Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Provision for Loan Losses Non-qualified option expense Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost, Nonqualified Stock Options Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost, Nonqualified Stock Options Restricted stock expense Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost, Restricted Stock Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Share-based Compensation Cost, Restricted Stock Deferred compensation Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Employee Compensation Deferred directors fees Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Directors Fees Deferred Tax Assets, Tax Deferred Expense, Compensation and Benefits, Directors Fees Loss carryforward Deferred Tax Assets, Operating Loss Carryforwards Non accrual interest Deferred Tax Assets, Deferred Income Foreclosed real estate writedowns Deferred Tax Assets, Foreclosed Real Estate Writedowns Deferred Tax Assets, Foreclosed Real Estate Writedowns Charitable contribution Deferred Tax Assets, Charitable Contribution Carryforwards Unrealized loss on securities available-for-sale Deferred Tax Assets, Unrealized Losses on Available-for-Sale Securities, Gross Other Deferred Tax Assets, Other Total deferred tax assets Deferred Tax Assets, Gross Components of Deferred Tax Liabilities [Abstract] Prepaid expenses Deferred Tax Liabilities, Prepaid Expenses Mortgage servicing rights Deferred Tax Liabilities, Mortgage Servicing Rights Office properties and equipment basis difference Deferred Tax Liabilities, Property, Plant and Equipment Federal Home Loan Bank stock basis difference Deferred Tax Liabilities, Federal Home Loan Bank Stock Deferred Tax Liabilities, Federal Home Loan Bank Stock Deferred Tax Liabilities, Other Comprehensive Income Deferred Tax Liabilities, Other Comprehensive Income Total deferred tax liabilities Deferred Tax Liabilities, Gross Valuation allowance Deferred Tax Assets, Valuation Allowance Net deferred tax asset Deferred Tax Assets, Net Regulatory Capital Requirements [Abstract] Regulatory Capital Regulatory Capital Requirements under Banking Regulations excluding Regulatory Actions [Text Block] Regulatory Capital Requirements under Banking Regulations excluding Regulatory Actions [Text Block] [Text Block] Deferred Compensation Arrangements [Abstract] Schedule of Deferred Compensation Arrangement with Individual, Postretirement Benefits [Table] Schedule of Deferred Compensation Arrangement with Individual, Postretirement Benefits [Table] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Title of Individual [Axis] Title of Individual [Axis] Relationship to Entity [Domain] Relationship to Entity [Domain] Director Director [Member] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Axis] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Axis] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Domain] Other Postretirement Benefits, Individual Contracts, Type of Deferred Compensation [Domain] Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits Deferred Compensation Arrangement with Individual, by Type of Compensation, Pension and Other Postretirement Benefits [Member] Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] Deferred Compensation Arrangement with Individual, Postretirement Benefits [Line Items] Deferred compensation arrangement, payment period Deferred Compensation Arrangement with Individual, Payment Period Deferred Compensation Arrangement with Individual, Payment period Deferred compensation liability Deferred Compensation Arrangement with Individual, Recorded Liability Deferred compensation expense Deferred Compensation Arrangement with Individual, Compensation Expense Cash surrender value of life insurance policies Cash Surrender Value of Life Insurance Retirement Benefits [Abstract] Share-based Arrangements with Employees and Nonemployees [Abstract] ESOP committed-to-be-released shares Employee Stock Ownership Plan (ESOP), Number of Committed-to-be-Released Shares ESOP compensation expense Employee Stock Ownership Plan (ESOP), Compensation Expense Employee Stock Ownership Plan (ESOP), Shares in ESOP [Abstract] Employee Stock Ownership Plan (ESOP), Shares in ESOP [Abstract] Employee Stock Ownership Plan (ESOP), Debt Structure, Indirect Loan, Amount Employee Stock Ownership Plan (ESOP), Debt Structure, Indirect Loan, Amount employee stock ownership plan, price per share employee stock ownership plan, price per share employee stock ownership plan, price per share Shares allocated to active participants Employee Stock Ownership Plan (ESOP), Number of Allocated Shares Shares committed to be released Employee Stock Ownership Plan (ESOP), Number of Released Shares Employee Stock Ownership Plan (ESOP), Number of Released Shares Unallocated shares Employee Stock Ownership Plan (ESOP), Number of Suspense Shares Total ESOP shares Employee Stock Ownership Plan (ESOP), Shares in ESOP Fair value of unallocated shares Employee Stock Ownership Plan (ESOP), Deferred Shares, Fair Value Guarantees [Abstract] Guarantees Guarantees [Text Block] Property, Plant and Equipment [Abstract] Office Properties and Equipment Property, Plant and Equipment and Leases of Lessee Disclosure [Text Block] Property, Plant and Equipment and Leases of Lessee Disclosure [Text Block] Earnings Per Share [Abstract] Earnings per Share Earnings Per Share [Text Block] Transfers and Servicing [Abstract] Schedule of assumptions for fair value as of balance sheet date of assets or liabilities that relate to transferor's continuing involvement Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Table Text Block] Servicing asset at amortized cost and schedule of valuation allowance for impairment of recognized servicing assets Servicing Asset at Amortized Cost and Schedule of Valuation Allowance for Impairment of Recognized Servicing Assets [Table Text Block] Servicing Asset at Amortized Cost and Schedule of Valuation Allowance for Impairment of Recognized Servicing Assets [Table Text Block] Loans and Leases Receivable Disclosure [Abstract] Summary of balances of loans Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Schedule of contractual aging of recorded investment in past due loans Past Due Financing Receivables [Table 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] Past due loans Nonperforming Financial Instruments [Member] Troubled debt restructurings Loans Financing Receivable, Recorded Investment [Line Items] Schedule of recorded investment by accrual status Schedule of Financing Receivables, Non Accrual Status [Table Text Block] Schedule of risk category of loans Financing Receivable Credit Quality Indicators [Table Text Block] Schedule of activity in the allowance for loan losses, by portfolio segment Allowance for Credit Losses on Financing Receivables [Table Text Block] Schedule of impaired loans Impaired Financing Receivables [Table Text Block] Schedule of loans modified in a TDR, by class Troubled Debt Restructurings on Financing Receivables [Table Text Block] Schedule of loans, related parties Schedule of Loans and Leases Receivable, Related Parties [Table Text Block] Schedule of Loans and Leases Receivable, Related Parties [Table Text Block] Investments, Debt and Equity Securities [Abstract] Schedule of amortized costs and fair values of securities available-for-sale Schedule of Available-for-sale Securities Reconciliation [Table Text Block] Schedule of amortized cost and estimated fair value of investment securities by contractual maturity Investments Classified by Contractual Maturity Date [Table Text Block] Schedule of investment securities in an unrealized loss position Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block] Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Property, Plant and Equipment [Table] Property, Plant and Equipment [Table] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Office building Office Building [Member] Office properties and equipment Office Properties and Equipment [Member] Office Properties and Equipment [Member] Property, Plant and Equipment [Line Items] Property, Plant and Equipment [Line Items] Operating Leases, Future Minimum Payments Receivable [Abstract] Operating Leases, Future Minimum Payments Receivable [Abstract] 2018 Operating Leases, Future Minimum Payments Receivable, Current 2019 Operating Leases, Future Minimum Payments Receivable, in Two Years 2020 Operating Leases, Future Minimum Payments Receivable, in Three Years 2021 Operating Leases, Future Minimum Payments Receivable, in Four Years 2022 Operating Leases, Future Minimum Payments Receivable, in Five Years Thereafter Operating Leases, Future Minimum Payments Receivable, Thereafter Total Operating Leases, Future Minimum Payments Receivable Gross rental income Rental Income, Nonoperating Rent expense Operating Leases, Rent Expense Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] 2018 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2019 Operating Leases, Future Minimum Payments, Due in Two Years 2020 Operating Leases, Future Minimum Payments, Due in Three Years 2021 Operating Leases, Future Minimum Payments, Due in Four Years Total Operating Leases, Future Minimum Payments Due Number of Properties Office Properties and Equipment Number of Properties Office Properties and Equipment Number of Properties Office Properties and Equipment Number of properties held for sale Number of Properties Held for Sale Number of Properties Held for Sale Condensed Financial Information of Parent Company Only Disclosure [Abstract] Condensed Income Statement [Table] Condensed Income Statement [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] Westbury Bank Parent Company [Member] Condensed Income Statements, Captions [Line Items] Condensed Income Statements, Captions [Line Items] Interest and other income Interest and Other Income Interest and other expense Interest and Other Expense Interest and Other Expense Loss before income tax benefit and equity in undistributed net income of subsidiary Income (Loss) from Subsidiaries, before Tax Income tax benefit Income (Loss) from Subsidiaries, Tax Expense (Benefit) Loss before equity in undistributed net income of subsidiary Income (Loss) from Subsidiaries, Net of Tax Equity in undistributed net income of subsidiary Equity in Undistributed Net Income (Loss) of Subsidiaries Equity in Undistributed Net Income (Loss) of Subsidiaries Net income Net Income (Loss) Attributable to Parent Schedule of Impaired Financing Receivable [Table] Schedule of Impaired Financing Receivable [Table] Receivable Type [Axis] Receivable Type [Axis] Receivable [Domain] Receivable [Domain] Single family Real Estate Single Family [Member] Represents information pertaining to the single family real estate. Multifamily Real Estate Multi Family [Member] Represents information pertaining to the multifamily real estate. Non-owner occupied Real estate Non-owner Occupied [Member] Real estate Non-owner Occupied [Member] Owner occupied Real Estate Owner Occupied [Member] Real Estate Owner Occupied Construction and land development Construction and Land Development [Member] Represents information pertaining to the construction and land development. Commercial Business Commercial Loan [Member] Consumer and Other Consumer Loan [Member] Impaired loans Financing Receivable, Impaired [Line Items] Unpaid Principal Balance Impaired Financing Receivable, Unpaid Principal Balance [Abstract] With no related allowance recorded Impaired Financing Receivable, with No Related Allowance, Unpaid Principal Balance With an allowance recorded Impaired Financing Receivable, with Related Allowance, Unpaid Principal Balance Total Impaired Financing Receivable, Unpaid Principal Balance Recorded Investment Impaired Financing Receivable, Recorded Investment [Abstract] With no related allowance recorded Impaired Financing Receivable, with No Related Allowance, Recorded Investment With an allowance recorded Impaired Financing Receivable, with Related Allowance, Recorded Investment Total Impaired Financing Receivable, Recorded Investment Allowance for Loan Losses Allocated Impaired Financing Receivable Related Allowance [Abstract] With an allowance recorded Impaired Financing Receivable, Related Allowance Average Recorded Investment Impaired Financing Receivable, Average Recorded Investment [Abstract] With no related allowance recorded Impaired Financing Receivable, with No Related Allowance, Average Recorded Investment With an allowance recorded Impaired Financing Receivable, with Related Allowance, Average Recorded Investment Total Impaired Financing Receivable, Average Recorded Investment Interest Income Recognized Impaired Financing Receivable, Interest Income, Cash Basis Method [Abstract] With no related allowance Impaired Financing Receivable with No Related Allowance Interest Income Amount of interest income, recognized on cash or accrual basis, on financing receivables, for which there is no related allowance for credit losses and are recognized as impaired. With related allowance Impaired Financing Receivable with Related Allowance Interest Income Amount of interest income on financing receivables, for which there is a related allowance for credit losses, recognized on a cash or accrual basis method of accounting that the financing receivables were impaired. Total Impaired Financing Receivable, Interest Income Amount of interest income recognized on a cash or accrual basis method of accounting that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired. Mortgage Servicing Rights Transfers and Servicing of Financial Assets [Text Block] Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization and principles of consolidation Consolidation, Policy [Policy Text Block] Jumpstart Our Business Startups Act Financial Statement Comparability Policy [Policy Text Block] Financial Statement Comparability Policy [Policy Text Block] Use of estimates Use of Estimates, Policy [Policy Text Block] Cash and cash equivalents Cash and Cash Equivalents, Policy [Policy Text Block] Securities Marketable Securities, Available-for-sale Securities, Policy [Policy Text Block] 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] Allowance for loan losses Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] Troubled debt restructurings Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block] Federal Home Loan Bank stock Federal Home Loan Bank stock [Policy Text Block] Federal Home Loan Bank stock [Policy Text Block] Foreclosed real estate Loans and Leases Receivable, Real Estate Acquired Through Foreclosure, Policy [Policy Text Block] Real estate held for investment/sale Real Estate Held for Development and Sale, Policy [Policy Text Block] Office properties and equipment Property, Plant and Equipment, Policy [Policy Text Block] Mortgage servicing rights and Transfers of financial assets Transfers and Servicing of Financial Assets, Policy [Policy Text Block] Employee stock ownership plan Employee Stock Ownership Plan (ESOP), Policy [Policy Text Block] Stock-based compensation Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block] Income taxes Income Tax, Policy [Policy Text Block] Derivative financial instruments and hedging activities Derivatives, Policy [Policy Text Block] Comprehensive income Comprehensive Income, Policy [Policy Text Block] Reclassification Reclassification, Policy [Policy Text Block] Segment reporting Segment Reporting, Policy [Policy Text Block] Recent accounting pronouncements New Accounting Pronouncements, Policy [Policy Text Block] Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Summary of financial impact of share-based payment plans Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block] Schedule of stock options Share-based Compensation, Stock Options, Activity [Table Text Block] Summary of valuation assumptions utilized for options Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Schedule of restricted stock shares and units Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block] Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Table] Schedule of Assumptions for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Table] Financial Instrument [Axis] Financial Instrument [Axis] Financial Instruments [Domain] Financial Instruments [Domain] Residential Mortgage Residential Mortgage [Member] Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items] Assumption for Fair Value as of Balance Sheet Date of Assets or Liabilities that relate to Transferor's Continuing Involvement [Line Items] Discount rates Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Discount Rate Prepayment speed range Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Prepayment Speed Weighted average default rate Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Weighted Average Default Rate Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Weighted Average Default Rate Derivative Instruments and Hedging Activities Disclosure [Abstract] Derivative Activities Derivative Instruments and Hedging Activities Disclosure [Text Block] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statement [Table] Condensed Balance Sheet Statements, Captions [Line Items] Condensed Balance Sheet Statements, Captions [Line Items] Assets Assets [Abstract] Cash and interest bearing deposits Cash and Cash Equivalents, at Carrying Value Investments Investments, Excluding Investments in Subsidiaries Investments, Excluding Investments in Subsidiaries Loan to ESOP Loan to Employee Stock Ownership Plan Loan to Employee Stock Ownership Plan Investment in subsidiary Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Other assets Other Assets Total assets Assets Liabilities and Stockholders' Equity Liabilities and Equity [Abstract] Other liabilities Other Liabilities Stockholders' equity Stockholders' Equity Attributable to Parent Total liabilities and stockholders' equity Liabilities and Equity Statement of Stockholders' Equity [Abstract] Statement [Table] Statement [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Preferred Stock Preferred Stock [Member] Common Stock Common Stock [Member] Additional Paid In Capital Additional Paid-in Capital [Member] Retained Earnings Retained Earnings [Member] Unearned ESOP Shares Unearned Employee Stock Ownership Plan Unearned ESOP Shares [Member] Represents information pertaining to unearned ESOP shares. Accumulated Other Comprehensive Income (Loss) AOCI Attributable to Parent [Member] Treasury Stock Treasury Stock [Member] Statement Statement [Line Items] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Balance, beginning of period Net income Other comprehensive income, net of tax Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Repurchase of 237,014 shares of common stock Stock Repurchased During Period, Value Exercise of 10,193 stock options Proceeds from Stock Options Exercised Stock based compensation expense Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Allocation, or commitment to be allocated, of 35,997 shares by ESOP Employee Stock Ownership Plan, Allocation of Stock, Value Employee Stock Ownership Plan, Allocation of Stock, Value Balance, end of period Deposits [Abstract] Related Party Deposit Liabilities Related Party Deposit Liabilities Time Deposits, Fiscal Year Maturity [Abstract] 2018 Time Deposit Maturities, Next Twelve Months 2019 Time Deposit Maturities, Year Two 2020 Time Deposit Maturities, Year Three 2021 Time Deposit Maturities, Year Four 2022 Time Deposit Maturities, Year Five Certificates of Deposit Time Deposits Real Estate [Abstract] Number of office properties designated as available for sale Number of Office Properties, Available-for-Sale Number of Office Properties, Available-for-Sale Valuation loss on real estate held for sale Impairment of Real Estate Banking and Thrift [Abstract] Foreclosed Real Estate Real Estate Owned [Text Block] Derivative [Table] Derivative [Table] Derivative, by Nature [Axis] Derivative Instrument [Axis] Derivative, Name [Domain] Derivative Contract [Domain] Swaps and Options Swaps and Options [Member] Swaps and Options [Member] Swap Swap [Member] Derivative [Line Items] Derivative [Line Items] Notional amount Derivative, Notional Amount Derivative liability, fair value Derivative Liability, Fair Value, Gross Liability Derivative asset, fair value Derivative Asset, Fair Value, Gross Asset Employee stock ownership plan (ESOP) disclosure Employee Stock Ownership Plan (ESOP) Disclosures [Table Text Block] Schedule of Available-for-sale Securities [Table] Schedule of Available-for-sale Securities [Table] 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] U.S. Government agency collateralized mortgage obligations Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] U.S. Government agency residential mortgage-backed securities Residential Mortgage Backed Securities [Member] U.S. Government agency commercial mortgage-backed securities Commercial Mortgage Backed Securities [Member] Securities Available for Sale Schedule of Available-for-sale Securities [Line Items] Available for Sale, Amortized Cost Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Rolling Maturity [Abstract] Due in one year or less Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Amortized Cost Basis Due after one year through five years Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Amortized Cost Basis Due after five years through ten years Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Amortized Cost Basis Due after ten years Available-for-sale Securities, Debt Maturities, Rolling after Year Ten, Amortized Cost Basis U.S. Government agency securities Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis Total Available-for-sale Debt Securities, Amortized Cost Basis Available for Sale, Fair Value Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity [Abstract] Due in one year or less Available-for-sale Securities, Debt Maturities, Next Rolling Twelve Months, Fair Value Due after one year through five years Available-for-sale Securities, Debt Maturities, Rolling Year Two Through Five, Fair Value Due after five years through ten years Available-for-sale Securities, Debt Maturities, Rolling Year Six Through Ten, Fair Value Due after ten years Available-for-sale Securities, Debt Maturities, Rolling after Year Ten, Fair Value U.S. Government agency securities Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value Securities available-for-sale Available-for-sale Securities Other disclosures Available-for-sale Securities, Other Disclosure Items [Abstract] Gross proceeds from sale of securities available-for-sale Proceeds from Sale of Available-for-sale Securities Gross realized gains on the sale of securities available-for-sale Available-for-sale Securities, Gross Realized Gains Gross realized losses on the sale of securities available-for-sale Available-for-sale Securities, Gross Realized Losses Securities pledged to secure treasury, tax, and loan deposits and other purposes Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment Held to maturity, amortized cost Held-to-maturity Securities, Debt Maturities, Amortized Cost, Rolling Maturity [Abstract] Due in one year or less Held-to-maturity Securities, Debt Maturities, within One Year, Net Carrying Amount Due after one year through five years Held-to-maturity Securities, Debt Maturities, after One Through Five Years, Net Carrying Amount Due after five years through ten years Held-to-maturity Securities, Debt Maturities, after Five Through Ten Years, Net Carrying Amount Due after ten years Held-to-maturity Securities, Debt Maturities, after Ten Years, Net Carrying Amount Amortized Cost Held-to-maturity Securities Amortized Cost Investment Securities, Amortized Cost Basis Investment Securities, Amortized Cost Basis Held-to-maturity, fair value Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract] Due in one year or less Held-to-maturity Securities, Debt Maturities, Next Twelve Months, Fair Value Due after one year through five years Held-to-maturity Securities, Debt Maturities, Year Two Through Five, Fair Value Due after five year through ten years Held-to-maturity Securities, Debt Maturities, Year Six Through Ten, Fair Value Due after ten years Held-to-maturity Securities, Debt Maturities, after Ten Years, Fair Value Fair Value Held-to-maturity Securities, Fair Value Investment Securities Investment Securities Investment Securities 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 Shares and Units Restricted Shares and Units [Member] Restricted Shares and Units [Member] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Shares and Units Outstanding at September 30, 2013 Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (shares and units) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Vested (shares and units) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Forfeited (in shares and units) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Shares and Units Outstanding at September 30, 2014 Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract] Outstanding at September 30, 2013 (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value Granted (in dollars 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 Vested (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value Forfeited (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value Outstanding at September 30, 2014 (in dollars per share) Nature of Operations and Summary of Significant Accounting Policies Basis of Presentation and Significant Accounting Policies [Text Block] Income Taxes Income Tax Disclosure [Text Block] Loans Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Schedule of financial instruments whose contract amounts represent credit risk Schedule of Fair Value, Off-balance Sheet Risks [Table Text Block] Current (benefit) expense Current Income Tax Expense (Benefit) Deferred (benefit)/expense Deferred Income Tax Expense (Benefit) Income tax expense (benefit) Income Tax Expense (Benefit) Number of shares purchased by ESOP Stock Issued During Period, Shares, Employee Stock Ownership Plan Number of shares repurchased during period Stock Repurchased During Period, Shares Number of restricted shares issued during period Stock Issued During Period, Shares, Restricted Stock Award, Gross Number of shares allocated by ESOP Employee Stock Ownership Plan, Shares Allocated During Period Employee Stock Ownership Plan, Shares Allocated During Period Exercised, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Schedule of Guarantor Obligations [Table] Schedule of Guarantor Obligations [Table] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Financial Guarantee Financial Guarantee [Member] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Maximum potential amount of future payments under limited recourse guarantee Guarantor Obligations, Maximum Exposure, Undiscounted Provision for loan losses Provision for Loan and Lease Losses Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Real Estate: Real Estate [Member] Consumer: Home equity lines of credit Home Equity Line of Credit [Member] Education Consumer Loan Education [Member] Represents the loan or extension of credit for education, excluding real estate. Other Consumer Portfolio Segment [Member] Loans Accounts, Notes, Loans and Financing Receivable [Line Items] Total Loans Loans and Leases Receivable, Gross Net deferred loan fees Loans and Leases Receivable, Deferred Income Allowance for loan losses Loans and Leases Receivable, Allowance Net Loans Loans and Leases Receivable, Net Amount Statement of Financial Position [Abstract] Held-to-maturity Securities, Fair Value Allowance for loan losses (in dollars) Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Preferred stock, shares authorized Preferred Stock, Shares Authorized Preferred stock, shares issued Preferred Stock, Shares Issued Preferred stock, shares outstanding Preferred Stock, Shares Outstanding Common stock, par value (in dollars per share) 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 Treasury stock, shares Treasury Stock, Shares Schedule of components of income tax expense (benefit) Schedule of Components of Income Tax Expense (Benefit) [Table Text Block] Schedule of effective income tax rate reconciliation Schedule of Effective Income Tax Rate Reconciliation [Table Text Block] Schedule of deferred tax assets and liabilities Schedule of Deferred Tax Assets and Liabilities [Table Text Block] Statement of Comprehensive Income [Abstract] Other comprehensive income, before tax: Other Comprehensive Income (Loss), Net of Tax [Abstract] Unrealized gains on available-for-sale securities Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, before Tax Income tax expense related to items of other comprehensive income Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Other comprehensive income, before tax Other Comprehensive Income (Loss), before Tax, Portion Attributable to Parent Income tax benefit (expense) related to items of other comprehensive income (loss) Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Other comprehensive income, net of tax Comprehensive income Comprehensive Income (Loss), Net of Tax, Attributable to Parent Income Statement [Abstract] Interest and dividend income: Interest and Dividend Income, Operating [Abstract] Loans Interest and Fee Income, Loans and Leases Investments - nontaxable Interest Income, Securities, Operating, Tax Exempt Investments - taxable Interest Income, Securities, Operating, Taxable 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 Short-term advances from the Federal Home Loan Bank Interest Expense, Federal Home Loan Bank and Federal Reserve Bank Advances, Short-term Long-term advances from the Federal Home Loan Bank Interest Expense, Federal Home Loan Bank and Federal Reserve Bank Advances, Long-term Line of credit Interest Expense, Other Total interest expense Interest Expense Net interest income before provision for loan losses Interest Income (Expense), Net Net interest income after provision for loan losses Interest Income (Expense), after Provision for Loan Loss Non-interest income: Noninterest Income [Abstract] Service fees on deposit accounts Fees and Commissions, Depositor Accounts Gain on sales of loans, net Gain (Loss) on Sales of Loans, Net Servicing fee income, net of amortization and impairment Bank Servicing Fees Insurance and securities sales commissions Insurance and Securities Sales Commissions Represents the amount of commission revenue on sale of insurance and securities. Gain on sales of securities Gain (Loss) on Sale of Securities, Net Gain on sales of branches and other assets Gain (Loss) on Disposition of Business Increase in cash surrender value of life insurance Bank Owned Life Insurance Income Rental income from real estate operations Other income Noninterest Income, Other Operating Income Total non-interest income Noninterest Income Non-interest expense: Noninterest Expense [Abstract] Salaries and employee benefits Labor and Related Expense Occupancy Occupancy, Net Data processing Information Technology and Data Processing Professional Fees Professional Fees FDIC insurance premiums Federal Deposit Insurance Corporation Premium Expense Other expenses Other Noninterest Expense Total non-interest expense Noninterest Expense Income before income tax expense (benefit) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Income tax expense (benefit) Earnings per share: Basic (in dollars per share) Earnings Per Share, Basic Diluted (in dollars per share) Earnings Per Share, Diluted Net income Net Income (Loss) Available to Common Stockholders, Basic Basic potential common shares: Weighted Average Number of Shares Outstanding, Basic [Abstract] Weighted average shares outstanding, shares Weighted Average Number of Shares Issued, Basic Weighted average unallocated Employee Stock Ownership Plan shares Weighted Average Number of Shares, Employee Stock Ownership Plan Shares Not Committed to be Released Basic weighted average shares outstanding, shares Weighted Average Number of Shares Outstanding, Basic Dilutive effect of equity awards Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted weighted average shares outstanding, shares Weighted Average Number of Shares Outstanding, Diluted Basic earnings per share (in dollars per share) Diluted earnings per share (in dollars per share) Foreclosed Real Estate [Roll Forward] Real Estate Owned, Foreclosure [Roll Forward] Real Estate Owned, Foreclosure [Roll Forward] Foreclosed real estate, beginning balance Real Estate Acquired Through Foreclosure Transfer of loans Real Estate Owned, Transfer to Real Estate Owned Writedown to realizable value Real Estate Owned, Write-downs Represents the amount of write-downs on other real estate added back to net income (loss) to arrive at cash flow from operating activities during the period. Proceeds on sale Proceeds from Sale of Foreclosed Assets Gain (loss) on sale Gains (Losses) on Sales of Other Real Estate Foreclosed real estate, ending balance Effective Income Tax Rate Reconciliation, Amount [Abstract] Computed expected tax expense Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount Net increase in cash surrender of life insurance Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Amount Tax-exempt interest, net Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount Increase from state income tax benefit, net Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Amount Equity incentive plans Effective Income Tax Rate Reconciliation, Equity incentive plans, amount Effective Income Tax Rate Reconciliation, Equity incentive plans, amount Other, net Effective Income Tax Rate Reconciliation, Other Adjustments, Amount Effective Income Tax Rate Reconciliation, Percent [Abstract] Effective Income Tax Rate Reconciliation, Percent [Abstract] Computed expected tax expense Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent Net increase in cash surrender of life insurance Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Percent Tax-exempt interest, net Effective Income Tax Rate Reconciliation, Tax Exempt Income, Percent Increase from state income tax benefit, net Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent Equity incentive plans Effective Income Tax Rate Reconcialition, Equity incentive plans, percentage Effective Income Tax Rate Reconcialition, Equity incentive plans, percentage Other, net Effective Income Tax Rate Reconciliation, Other Adjustments, Percent Income tax rate percentage Effective Income Tax Rate Reconciliation, Percent Schedule of actual capital amounts and ratios and those required by the above regulatory standards Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table Text Block] Schedule of reconciliation of the Bank's stockholders' equity to regulatory capital Schedule of Reconciliation of Stockholders Equity to Regulatory Capital [Table Text Block] Tabular disclosure of reconciliation of stockholders' equity to regulatory capital. Cash and Cash Equivalents [Abstract] Schedule of Cash and Cash Equivalents [Table] Schedule of Cash and Cash Equivalents [Table] Legal Entity [Axis] Legal Entity [Axis] Entity [Domain] Entity [Domain] Westbury Bank Westbury Bank FSB [Member] Represents information pertaining to Westbury Bank, FSB. Cash and Cash Equivalents [Line Items] Cash and Cash Equivalents [Line Items] Cash and due from banks Cash and Due from Banks Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Number of wholly-owned limited liability corporations (included in financial statements) Number of Wholly-Owned Limited Liability Corporations Number of Wholly-Owned Limited Liability Corporations Number of operating segments Number of Operating Segments Allowance for loan losses Allowance for Loan and Lease Losses [Roll Forward] Balance, beginning Loans charged-off Allowance for Loan and Lease Losses, Write-offs Recoveries Allowance for Loan and Lease Loss, Recovery of Bad Debts Balance, ending Period-ended amount allocated for: Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract] Individually evaluated for impairment Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment Collectively evaluated for impairment Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment Ending Balance Loans: Loans and Leases Receivable, Gross, Carrying Amount [Abstract] Individually evaluated for impairment Financing Receivable, Individually Evaluated for Impairment Collectively evaluated for impairment Financing Receivable, Collectively Evaluated for Impairment Total Defined Contribution Plan [Abstract] Defined Contribution Plan [Abstract] Participants minimum percent of contribution to the plan Defined Contribution Plan, Minimum Annual Contributions Per Employee, Percent Minimum percentage of employee gross pay the employee may contribute to a defined contribution plan. Participants maximum percent of contribution to the plan Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent Defined contribution plan expense Defined Contribution Plan, Cost Real Estate Held for Sale and Branch Closings Real Estate Held-for-sale Disclosure [Text Block] Real Estate Held-for-sale Disclosure [Text Block] Schedule of composition of deposits Schedule of Deposits [Table Text Block ] Tabular disclosure of deposit liabilities held by the entity. Schedule of maturities of time deposits Schedule of Maturities of Time Deposits [Table Text Block] Schedule of Maturities of Time Deposits [Table Text Block] Income Statement Location [Axis] Income Statement Location [Axis] Income Statement Location [Domain] Income Statement Location [Domain] Furniture and equipment and occupancy expenses Furniture and Equipment and Occupancy Expenses [Member] Furniture and Equipment and Occupancy Expenses [Member] Land and land improvements Land and Land Improvements [Member] Office buildings and improvements Building and Building Improvements [Member] Furniture and equipment Furniture and equipment [Member] Furniture and equipment [Member] Leasehold improvements Leasehold Improvements [Member] Office properties and equipment, gross Property, Plant and Equipment, Gross Less accumulated depreciation and amortization Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Office properties and equipment, net Property, Plant and Equipment, Net Depreciation and amortization expense Depreciation, Depletion and Amortization 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] Nonrecurring basis Fair Value, Measurements, Nonrecurring [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Amount Reported Value Measurement [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Fair Value, Inputs, Level 1 [Member] Fair Value, Inputs, Level 1 [Member] Significant Other Observable Inputs (Level 2) Fair Value, Inputs, Level 2 [Member] Significant Other Unobservable Inputs (Level 3) Fair Value, Inputs, Level 3 [Member] Assets measured at fair value on a nonrecurring basis Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Impaired loans Impaired Financing Receivable, Fair Value Disclosure Fair value of impaired financing receivables as of the balance sheet date. Foreclosed real estate Real Estate Acquired Through Foreclosure, Fair Value Disclosure Real Estate Acquired Through Foreclosure, Fair Value Disclosure Mortgage servicing rights Servicing Asset at Fair Value, Amount Real Estate Held-for-sale Real Estate Held-for-sale Impaired loans, valuation allowance Mortgage servicing rights, valuation allowance Valuation Allowance for Impairment of Recognized Servicing Assets, Balance Deferred Compensation Compensation and Employee Benefit Plans, Other than Share-based Compensation [Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Estimated Fair Value Estimate of Fair Value Measurement [Member] Quoted Prices in Active Markets for Identical Assets (Level 1) Fair Value of Financial Assets and Financial Liabilities Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Financial assets Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract] Cash and cash equivalents Cash and Cash Equivalents, Fair Value Disclosure Securities available for sale Held-to-maturity Securities Loans, net Loans Receivable, Fair Value Disclosure Loans held for sale, net Loans Held-for-sale, Fair Value Disclosure Federal Home Loan Bank stock Federal Home Loan Bank Stock Mortgage servicing rights Accrued interest receivable Interest Receivable Derivative asset Embedded Derivative, Fair Value of Embedded Derivative Asset Financial liabilities Financial Instruments, Financial Liabilities, Balance Sheet Groupings [Abstract] Deposits Deposits, Fair Value Disclosure Short-term advances from Federal Home Loan Bank Advances, Fair Value Disclosure Long-term advances from Federal Home Loan Bank Federal Home Loan Bank Borrowings, Fair Value Disclosure Advance payments by borrowers for property taxes and insurance Advance Payments by Borrowers for Taxes and Insurance Accrued interest payable Interest Payable Derivative liability Embedded Derivative, Fair Value of Embedded Derivative Liability Number of Options Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Options outstanding, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Expired or canceled, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Expirations in Period Forfeited, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures in Period Options outstanding, shares Options exercisable, shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] Beginning (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Expired or canceled (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price Forfeited (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price Ending (in dollars per share) Exercisable (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Weighted Average Remaining Contractual Term, Options outstanding (years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Weighted Average Remaining Contractual Term, Exercisable (years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Aggregate intrinsic value, options outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Aggregate intrinsic value, exercisable Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Compensation Equity Plans Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Regulatory Capital Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] CET1 capital (to risk-weighted assets), Amount Common Equity Tier One Risk Base Capital, Actual [Abstract] Common Equity Tier One Risk Base Capital, Actual [Abstract] Actual Common Equity Tier 1 Risk Based Capital Common Equity Tier 1 Risk Based Capital For Capital Adequacy Purposes Common Equity Tier One Risk Based Capital Required for Capital Adequacy Credit Common Equity Tier One Risk Based Capital Required for Capital Adequacy Credit For Capital Adequacy Credit with Capital Buffer Common Equity Tier One Risk Based Capital Required for Capital Adequacy Credit with Capital Buffer Common Equity Tier One Risk Based Capital Required for Capital Adequacy Credit with Capital Buffer To be Well Capitalized Under Corrective Action Provisions Common Equity Tier One Risk Based Capital Required to be Well Capitalized Common Equity Tier One Risk Based Capital Required to be Well Capitalized CET1 capital (to risk-weighted assets), Ratio Common Equity Tier One Risk Base Capital, Ratio [Abstract] Common Equity Tier One Risk Base Capital, Ratio [Abstract] Actual (as a percent) Common Equity Tier One Risk Based Capital to Risk Weighted Assets Common Equity Tier One Risk Based Capital to Risk Weighted Assets For Capital Adequacy Purposes (as a percent) Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets For Capital Adequacy with Capital Buffer (as a percent) Common Equity Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer to Risk Weighted Assets Common Equity Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer to Risk Weighted Assets To be Well Capitalized Under Prompt Corrective Action Provisions (as a percent) Common Equity Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Common Equity Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Total capital (to risk-weighted assets), Amount Capital [Abstract] Actual Capital For Capital Adequacy Purposes Capital Required for Capital Adequacy For Capital Adequacy with Capital Buffer Capital Required for Capital Adequacy with Capital Buffer Capital Required for Capital Adequacy with Capital Buffer To be Well Capitalized Under Prompt Corrective Action Provisions Capital Required to be Well Capitalized Total capital (to risk-weighted assets), Ratio Capital to Risk Based Ratios [Abstract] Actual (as a percent) Capital to Risk Weighted Assets For Capital Adequacy Purposes (as a percent) Capital Required for Capital Adequacy to Risk Weighted Assets For Capital Adequacy with Capital Buffer (as a percent) Capital Required for Capital Adequacy with Capital Buffer to Risk Weighted Assets Capital Required for Capital Adequacy with Capital Buffer to Risk Weighted Assets To be Well Capitalized Under Prompt Corrective Action Provisions (as a percent) Capital Required to be Well Capitalized to Risk Weighted Assets Tier 1 capital (to risk-weighted assets), Amount Tier One Risk Based Capital [Abstract] Actual Tier One Risk Based Capital For Capital Adequacy Purposes Tier One Risk Based Capital Required for Capital Adequacy For Capital Adequency with Capital Buffer Tier One Risk Basked Capital Required fro Capital Adequency with Capital Buffer Tier One Risk Basked Capital Required fro Capital Adequency with Capital Buffer To be Well Capitalized Under Prompt Corrective Action Provisions Tier One Risk Based Capital Required to be Well Capitalized Tier 1 capital (to risk-weighted assets), Ratio Risk Based Ratios [Abstract] Actual (as a percent) Tier One Risk Based Capital to Risk Weighted Assets For Capital Adequacy Purposes (as a percent) Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets For Capital Adequacy with Capital Buffer (as a percent) Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer to Risk Weighted Asset Tier One Risk Based Capital Required for Capital Adequacy with Capital Buffer to Risk Weighted Asset To be Well Capitalized Under Prompt Corrective Action Provisions (as a percent) Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets Tier 1 capital (to adjusted total assets), Amount Tier One Leverage Capital [Abstract] Actual Tier One Leverage Capital For Capital Adequacy Purposes Tier One Leverage Capital Required for Capital Adequacy To be Well Capitalized Under Prompt Corrective Action Provisions Tier One Leverage Capital Required to be Well Capitalized Tier 1 capital (to adjusted total assets), Ratio Leverage Ratios [Abstract] Actual (as a percent) Tier One Leverage Capital to Average Assets For Capital Adequacy Purposes (as a percent) Tier One Leverage Capital Required for Capital Adequacy to Average Assets To be Well Capitalized Under Prompt Corrective Action Provisions (as a percent) Tier One Leverage Capital Required to be Well Capitalized to Average Assets Reconciliation of stockholders' equity to regulatory capital Reconciliation of Stockholders Equity to Regulatory Capital [Abstract] Stockholders' equity of the Bank Less: Disallowed servicing assets Servicing Asset Unrealized loss on securities Unrealized Gain (Loss) on Securities Disallowed investment in subsidiary Disallowed deferred tax assets Deferred Tax Assets, Net of Valuation Allowance Tier 1 and tangible capital Tangible Capital Plus: Allowable general valuation allowances Regulatory Capital Allowable Valuation Allowances Represents the regulatory capital valuation allowance allowed. Risk-based capital Deposits Deposit Liabilities Disclosures [Text Block] Condensed Parent Company Financial Information Condensed Financial Information of Parent Company Only Disclosure [Text Block] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Schedule of Financing Receivable, Troubled Debt Restructurings [Table] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Axis] Financing Receivable Portfolio Segment [Domain] Financing Receivable Portfolio Segment [Domain] Troubled debt restructured loans Financing Receivable, Modifications [Line Items] Troubled debt restructurings - accrual Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing Troubled debt restructurings - nonaccrual Financing Receivable, Recorded Investment, Nonaccrual Status Troubled debt restructurings Financing Receivable, Modifications, Recorded Investment Modified Trouble Debt Restructurings [Abstract] Modified Trouble Debt Restructurings [Abstract] Modified Trouble Debt Restructurings [Abstract] Number of Modifications Financing Receivable, Modifications, Number of Contracts Balance in the ALLL, At Period End Allowance for Credit Losses, Change in Method of Calculating Impairment Loans Modified in a Trouble Debt Restructuring [Abstract] Loans Modified in a Trouble Debt Restructuring [Abstract] Loans Modified in a Trouble Debt Restructuring [Abstract] Other Financing Receivable, Modifications, Other The amount of the outstanding recorded investment for financing receivables that have been modified by troubled debt restructurings related to other changes. Number of re-defaults of TDR Financing Receivable, Modifications, Subsequent Default, Number of Contracts Loans and Leases Receivable, Related Parties [Roll Forward] Loans outstanding to officers, employees, directors, and their associates Loans and Leases Receivable, Related Parties Balance, beginning New loans originated Loans and Leases Receivable, Related Parties, Additions Draws on lines of credit Loans and Leases Receivable, Related Parties, Amount Drawn Upon During Period Loans and Leases Receivable, Related Parties, Amount Drawn Upon During Period Principal repayments Loans and Leases Receivable, Related Parties, Proceeds Other Loans and Leases Receivable, Related Parties, Other Loans and Leases Receivable, Related Parties, Other Balance, ending Advances from Federal Home Loan Banks [Abstract] Advances From the Federal Home Loan Bank Federal Home Loan Bank Advances, Disclosure [Text Block] Risk-free interest rate Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Expected volatility of Company's stock Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Expected dividend yield Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected life of options (years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Weighted average fair value per option of options granted during the year Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Federal Home Loan Bank, Advances, Fiscal Year Maturity [Abstract] 2018 Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months 2019 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Two 2020 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Three 2021 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Four 2022 Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Five Thereafter Federal Home Loan Bank, Advances, Maturities Summary, Due after Year Five Long-term advances from Federal Home Loan Bank Long-term Federal Home Loan Bank Advances U.S. Government and agency securities US Government Agencies Debt Securities [Member] Municipal securities-tax exempt Nontaxable Municipal Bonds [Member] Municipal securities-taxable Taxable Municipal Bonds [Member] Corporate securities Corporate Debt Securities [Member] Amortized Cost Available-for-sale Securities, Amortized Cost Basis 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 Held-to-maturity Securities [Abstract] Held-to-maturity Securities [Abstract] Held to Maturity, Accumulated Gross Unrealized Loss, before Tax Held to Maturity, Accumulated Gross Unrealized Loss, before Tax Held to Maturity, Accumulated Gross Unrealized Loss, before Tax Held to Maturity Securities, Accumulated Gross Unrealized Gain, before Tax Instant Held to Maturity Securities, Accumulated Gross Unrealized Gain, before Tax Instant Held to Maturity Securities, Accumulated Gross Unrealized Gain, before Tax Instant Total Investment Securities Investment Securities [Abstract] Investment Securities [Abstract] Investment Securities, Accumulated Gross Unrealized Gain, before Tax Investment Securities, Accumulated Gross Unrealized Gain, before Tax Investment Securities, Accumulated Gross Unrealized Gain, before Tax Investment Securities, Accumulated Gross Unrealized Loss, before Tax Investment Securities, Accumulated Gross Unrealized Loss, before Tax Investment Securities, Accumulated Gross Unrealized Loss, before Tax Investment Securities Schedule of Fair Value, Off-balance Sheet Risks [Table] Schedule of Fair Value, Off-balance Sheet Risks [Table] Home Equity Loan [Member] Home Equity Loan [Member] Commercial Loan [Member] Fixed rate Fixed Rate Commitments to Extend Credit [Member] Represents information pertaining to fixed rate commitments to extend mortgage credit. Adjustable rate Adjustable Rate Commitments to Extend Credit [Member] Represents information pertaining to adjustable rate commitments to extend mortgage credit. Unused commercial loan lines of credit Unused lines of Credit [Member] Standby letters of credit Standby Letters of Credit [Member] Commitment to sell loans Loan Sale Commitments [Member] Represents the commitment to sale loans to third party. Financial Instruments with Off-Balance Sheet Risk Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] Financial instruments whose contract amounts represent credit risk Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability Maximum period of letters of credit primarily issued to support public and private borrowing arrangements Maximum Period of Standby Letters of Credit Primarily Issued to Support Public and Private Borrowing Arrangements Represents the maximum period of standby letters of credit primarily issued to support public and private borrowing arrangements. Liabilities recorded for company's potential obligations Fair Value Disclosure, Off-balance Sheet Risks, Liability Recorded for Potential Obligations Fair Value Disclosure, Off-balance Sheet Risks, Liability Recorded for Potential Obligations Schedule of Non-Cancelable Lease Revenue [Table] Schedule of Non-Cancelable Lease Revenue [Table] Schedule of Non-Cancelable Lease Revenue [Table] Real Estate Investment Partnership Expense Real Estate Investment Partnership Expense [Member] Real Estate Investment Partnership Expense [Member] Land Land [Member] Schedule of Non-Cancelable Lease Revenue [Line Items] Schedule of Non-Cancelable Lease Revenue [Line Items] [Line Items] for Schedule of Non-Cancelable Lease Revenue [Table] Depreciation expense Depreciation Total cost of stock grant plan during the year Allocated Share-based Compensation Expense, Stock Grant Allocated Share-based Compensation Expense, Stock Grant Total cost of stock option plan during the year Allocated Share-based Compensation Expense, Stock Options Allocated Share-based Compensation Expense, Stock Options Total cost of share-based payment plans during the year Allocated Share-based Compensation Expense Amount of related income tax benefit recognized in income Employee Service Share-based Compensation, Tax Benefit from Compensation Expense Pass Pass Excluding Performing Nonperforming Loans [Member] A category of financing receivables not considered to be special mention, substandard, doubtful, and loss receivables exclusive of loans classified as performing or nonperforming. Watch Watch Excluding Performing Nonperforming Loans [Member] A category of financing receivables with potential weaknesses that deserve management's close attention. Excludes loans classified as performing or nonperforming. Special Mention Special Mention Excluding Performing Nonperforming Loans [Member] A category of financing receivables, excluding loans classified as performing or nonperforming, considered to have potential weaknesses that deserve management's close attention. If left uncorrected, those potential weaknesses may result in a deterioration of the repayment prospects for the asset or of the creditor's position at some future date. Substandard Substandard Excluding Performing Nonperforming Loans [Member] A category of financing receivables, excluding loans classified as performing or nonperforming, that are inadequately protected by the current sound worth and paying capacity of the obligor or of the collateral pledged, if any. Loans so classified have a well-defined weakness or weaknesses that jeopardize the liquidation of the debt. They are characterized by the distinct possibility that the creditor will sustain some loss if the deficiencies are not corrected. Doubtful Doubtful [Member] Total Investment Securities Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Office properties and improvements Investment Building and Building Improvements Less-accumulated depreciation and amortization Real Estate Investment Property, Accumulated Depreciation Real Estate Investments, Net Real Estate Investments, Net Real Estate Held for Investment Real Estate Held-for-investment Disclosure [Text Block] Real Estate Held-for-investment Disclosure [Text Block] Document and Entity Information Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Document Type Document Type Document Period End Date Document Period End Date Amendment Flag Amendment Flag Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus Document Fiscal Period Focus Entity Well-known Seasoned Issuer Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Voluntary Filers Entity Current Reporting Status Entity Current Reporting Status Entity Public Float Entity Public Float Employee Benefit Plans Defined Contribution Plans and Employee Stock Ownership Plans [Text Block] Defined Contribution Plans and Employee Stock Ownership Plans [Text Block] Corporate securities Total temporary impaired securities Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Abstract] Less than 12 Months, Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value 12 Months or Longer, Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value Total, Fair Value Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value Less than 12 Months-Unrealized Loss Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss 12 Months or Longer-Unrealized Loss Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss Total Accumulated Unrealized Loss Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss Number of securities in an unrealized loss position, greater than twelve months Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year Number of securities in an unrealized loss position, less than twelve months Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Westbury Bancorp Inc 2014 Equity Incentive Plan Westbury Bancorp Inc 2014 Equity Incentive Plan [Member] Westbury Bancorp Inc 2014 Equity Incentive Plan [Member] Stock options Employee Stock Option [Member] Shares authorized for issuance Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized Shares available for future grant Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant-Stock Grants Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant-Stock Grants Stock options available for future grants Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant-Stock Options Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant-Stock Options stock based compensation vesting period-minimum stock based compensation vesting period-minimum stock based compensation vesting period-minimum stock option vesting period-maximum stock option vesting period-maximum stock option vesting period-maximum stock grants vesting period stock grants vesting period stock grants vesting period Intrinsic value of options exercised Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value Intrinsic value of restricted shares vested Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested Total unrecognized compensation cost Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Recognition period for compensation expense Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Recurring basis Fair Value, Measurements, Recurring [Member] Assets and liabilities measured at fair value Assets Assets, Fair Value Disclosure [Abstract] Derivative Asset, Fair Value, Gross Asset Derivatives Derivative Liability, Fair Value, Gross Liability Liabilities Liabilities, Fair Value Disclosure [Abstract] Derivatives Schedule of calculated earnings per share, basic and diluted Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Operating Loss Carryforwards [Table] Operating Loss Carryforwards [Table] Income Tax Authority [Axis] Income Tax Authority [Axis] Income Tax Authority [Domain] Income Tax Authority [Domain] State and Local Jurisdiction State and Local Jurisdiction [Member] Internal Revenue Service (IRS) Internal Revenue Service (IRS) [Member] Operating Loss Carryforwards [Line Items] Operating Loss Carryforwards [Line Items] Operating loss carryforwards Operating Loss Carryforwards Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax Deferred Tax Assets, Valuation Allowance Operating loss carryforwards, valuation allowance Operating Loss Carryforwards, Valuation Allowance Deferred income taxes provided, bad debt loss Deferred Income Tax Liability, Bad Debt Reserve for Tax Purposes of Qualified Lender Deferred Income Tax Liability, Bad Debt Reserve for Tax Purposes of Qualified Lender Bad debt reserve for tax purposes of qualified lender Bad Debt Reserve forTax Purposes of Qualified Lender Deferred tax liability not recognized, amount of unrecognized deferred tax liability, bad debt reserve for tax purposes of qualified lender Deferred Tax Liability Not Recognized, Amount of Unrecognized Deferred Tax Liability, Bad Debt Reserve for Tax Purposes of Qualified Lender Negotiable order for withdrawal accounts: Deposits, by Component, Alternative [Abstract] Non-interest bearing Noninterest-bearing Domestic Deposit, Demand Interest bearing Interest-bearing Domestic Deposit, Negotiable Order of Withdrawal (NOW) Gross total Deposits, Negotiable Order of Withdrawal (NOW) Passbook and Statement Savings Deposits, Savings Deposits Variable Rate Money Market Accounts Deposits, Money Market Deposits Certificates of Deposit Deposits Deposits Negotiable order for withdrawal accounts: Percentage of Negotiable Order for Withdrawal Accounts [Abstract] Noninterest bearing (as a percent) Noninterest Bearing Domestic Deposit Negotiable Order of Withdrawal NOW Percentage Represents the percentage of noninterest-bearing domestic negotiable order of withdrawal (NOW) demand deposit liabilities to total deposit liabilities. Interest bearing (as a percent) Interest Bearing Domestic Deposit Negotiable Order of Withdrawal NOW Percentage Represents the percentage of interest-bearing domestic negotiable order of withdrawal (NOW) demand deposit liabilities to total deposit liabilities. Gross total (as a percent) Percentage of Negotiable Order for Withdrawal Accounts Represents the percentage of domestic negotiable order of withdrawal (NOW) demand deposit liabilities to total deposit liabilities. Passbook and Statement Savings (as a percent) Percentage of Passbook and Statement Savings Deposit Represents the percentage of passbook and statement savings deposit liabilities to total deposit liabilities. Variable Rate Money Market Accounts (as a percent) Percentage of Variable Rate Money Market Accounts Represents the percentage of variable rate money market accounts deposit liabilities to total deposit liabilities. Certificates of Deposit (as a percent) Percentage of Certificate Accounts Represents the percentage of time deposit liabilities to total deposit liabilities. Deposits (as a percent) Percentage of Deposits Represents the percentage of deposit liabilities to total deposit liabilities. Certificates of Deposit over one hundred thousand dollars Time Deposits, $100,000 or More Certificates of Deposit over two hundred fifty thousand dollars Time Deposits, $250,000 or More Time Deposits, $250,000 or More Schedule of assets and liabilities measured at fair value on a recurring basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] Schedule of assets measured at fair value on a nonrecurring basis Fair Value Measurements, Nonrecurring [Table Text Block] Schedule of estimated fair values and related carrying amounts of the entity's financial instruments