Financial Instrument [Axis] US Government Agencies Debt Securities [Member] US States and Political Subdivisions Debt Securities [Member] Preferred Stock [Member] Collateralized Mortgage Backed Securities [Member] Equity Securities [Member] Corporate Debt Securities [Member] Fair Value Measurement [Axis] Estimate of Fair Value Measurement [Member] Reported Value Measurement [Member] Fair Value, Hierarchy [Axis] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 1 [Member] Asset-backed Securities [Member] Federal Home Loan Bank Branch [Axis] Federal Home Loan Bank of Boston [Member] Equity Components [Axis] Unearned Compensation Restricted Stock [Member] Retained Earnings [Member] Deferred Compensation, Share-based Payments [Member] AOCI Attributable to Parent [Member] Additional Paid-in Capital [Member] Common Stock [Member] Financing Receivable Portfolio Segment [Axis] Unallocated Financing Receivables [Member] Home Equity Loans And Lines Of Credit Portfolio Segment [Member] Construction Portfolio Segment [Member] Residential Portfolio Segment [Member] Consumer Portfolio Segment [Member] Commercial Real Estate Portfolio Segment [Member] Option Indexed to Issuer's Equity, Type [Axis] Employee Stock Option [Member] Plan Name [Axis] Two Thousand And Fifteen Equity Incentive Plan [Member] Property, Plant and Equipment, Type [Axis] Furniture and Fixtures [Member] Range [Axis] Minimum [Member] Maximum [Member] Building [Member] Financing Receivables, Period Past Due [Axis] Financing Receivables, 60 to 89 Days Past Due [Member] Financing Receivables, 30 to 59 Days Past Due [Member] Financing Receivables, Equal to Greater than 90 Days Past Due [Member] Class of Financing Receivable, Type [Axis] One Four Family Residential Loans [Member] One to Four Family Residential Real Estate Loans [Member] Internal Credit Assessment [Axis] Loans Receivables Related Risk Rating Six [Member] Credit Loss Status [Axis] Financial Asset Acquired with Credit Deterioration [Member] Special Mention [Member] Loans Receivables Related Risk Rating Seven [Member] Data Processing Equipment [Member] Land [Member] Construction in Progress [Member] Lender Name [Axis] Cooperative Central Bank [Member] Long-term Debt, Type [Axis] Construction Loans [Member] Unused lines of Credit [Member] Loan Origination Commitments [Member] Reclassification out of Accumulated Other Comprehensive Income [Axis] Reclassification out of Accumulated Other Comprehensive Income [Member] Regulatory Agency [Axis] Capital Regulations [Member] Award Date [Axis] July One To Three One Two Zero One Eight [Member] August One To Three One Two Zero One Eight [Member] September One To Three Zero Two Zero One Eight [Member] Consolidated Entities [Axis] Subsidiaries [Member] Legal Entity [Axis] MelroseCooperativeBankMember Mortgage-backed Securities, Issued by Private Enterprises [Member] Melrose Cooperative Bank Foundation [Member] Melrose Bancorp, Inc. [Member] Retirement Plan Name [Axis] Pentegra Plan [Member] Supplemental Executive Retirement Benefits [Member] Award Type [Axis] Restricted Stock Units (RSUs) [Member] Restricted Stock [Member] January One To Three One Two Zero One Eight [Member] February One Through Two Eight Two Zero One Eight [Member] March One Through Three One Two Zero One Eight [Member] April One To Three Zero Two Zero One Eight [Member] May One To Three One Two Zero One Eight [Member] June One To Three Zero Two Zero One Eight [Member] October One To Three One Two Zero One Eight [Member] November One To Three Zero Two Zero One Eight [Member] December One To Three One Two Zero One Eight [Member] Subsequent Event Type [Axis] Subsequent Event [Member] Parent Company [Member] Minimum [Member] Document And Entity Information [Abstract] Entity Registrant Name Entity Central Index Key Trading Symbol Amendment Flag Current Fiscal Year End Date Document Type Document Period End Date Document Fiscal Period Focus Document Fiscal Year Focus Entity Well-known Seasoned Issuer Entity Voluntary Filers Entity Current Reporting Status Entity Filer Category Entity Shell Company Entity Ex Transition Period Entity Small Business Entity Emerging Growth Company Entity Public Float Entity Common Stock, Shares Outstanding Statement of Financial Position [Abstract] ASSETS Cash and due from banks Money market funds Federal funds sold Cash and cash equivalents Interest-bearing time deposits with other banks Investments in available-for-sale securities, at fair value Federal Home Loan Bank stock, at cost Loans, net of allowance for loan losses of $1,323 at December 31, 2018 and $1,134 at December 31, 2017 Premises and equipment, net Co-operative Central Bank deposit Bank-owned life insurance Accrued interest receivable Deferred tax asset, net Other assets Total assets LIABILITIES AND STOCKHOLDERS' EQUITY Deposits: Noninterest-bearing Interest-bearing Total deposits Federal Home Loan Bank advances Other liabilities Total liabilities Stockholders' equity: Common stock, par value $0.01 per share, authorized 15,000,000 shares; issued and outstanding 2,573,024 shares at December 31, 2018 and 2,600,743 shares at December 31, 2017 Additional paid-in capital Retained earnings Unearned compensation - ESOP (188,638 shares unallocated at December 31, 2018 and 196,184 shares unallocated at December 31, 2017) Unearned compensation - restricted stock Accumulated other comprehensive (loss)/income Total stockholders' equity Total liabilities and stockholders' equity Allowance for loan losses Common stock, par value Common stock, shares authorized Common stock, shares issued ESOP number of shares unallocated Income Statement [Abstract] Interest and dividend income: Interest and fees on loans Interest and dividends on securities: Taxable Tax-exempt Other interest Total interest and dividend income Interest expense: Interest on deposits Interest on Federal Home Loan Bank advances Total interest expense Net interest and dividend income Provision for loan losses Net interest and dividend income after provision for loan losses Noninterest income: Fees and service charges Gain on sales and calls of available-for-sale securities, net Income on bank-owned life insurance Other income Total noninterest income Noninterest expense: Salaries and employee benefits Occupancy expense Equipment expense Data processing expense Advertising expense Printing and supplies FDIC assessment Audits and examinations Other professional services Other expense Total noninterest expense Income before income tax expense Income tax expense Net income Weighted average common shares outstanding: Basic Diluted Earnings per share: Basic Diluted Statement of Comprehensive Income [Abstract] Net income Other comprehensive loss, net of tax: Net unrealized holding (loss) gain on available-for-sale securities Reclassification adjustment for net realized gains included in net income Other comprehensive loss before income tax effect Income tax benefit Other comprehensive loss, net of tax Comprehensive income Statement [Table] Statement [Line Items] Common Stock Additional Paid-in-Capital Retained Earnings Unearned Compensation- ESOP Unearned Compensation - Restricted Stock Accumulated Other Comprehensive (Loss)/Income Beginning balance Beginning balance, shares Other comprehensive loss, net of tax Dividends paid ($0.34 per share) Restricted stock award expense Stock option expense Repurchase of common stock Repurchase of common stock, shares Common stock held by ESOP committed to be allocated (7,544 shares annually) Shares repurchased for tax withholdings on stock-based compensation Shares repurchased for tax withholdings on stock-based compensation, shares Stock options exercised Stock options exercised, shares Reclassification adjustment for stranded accumulated other comprehensive income due to tax rate change Ending balance Ending balance, shares Statement of Stockholders' Equity [Abstract] Common stock held by ESOP committed to be allocated, shares Dividends paid per share Statement of Cash Flows [Abstract] Cash flows from operating activities: Adjustments to reconcile net income to net cash provided by operating activities: Amortization of securities, net of accretion Gain on sales and calls of available-for-sale securities, net Provision for loan losses Change in net deferred loan fees/costs Change in unamortized premiums Depreciation Increase in accrued interest receivable Increase in other assets Increase in other liabilities Deferred tax expense Income on bank-owned life insurance ESOP expense Stock-based compensation expense Net cash provided by operating activities Cash flows from investing activities: Purchases of available-for-sale securities Proceeds from sales of available-for-sale securities Proceeds from maturities and calls of available-for-sale securities Purchase of interest-bearing time deposits with other banks Purchases of Federal Home Loan Bank stock Decrease (Increase) in Cooperative Central Bank deposit Loan originations and principal collections, net Loans purchased Capital expenditures Premiums paid on bank-owned life insurance Net cash used in investing activities Cash flows from financing activities: Net increase in demand deposits, NOW and savings accounts Net increase in time deposits Proceeds from Federal Home Loan Bank advances Repayment of advances from Federal Home Loan Bank Cash dividend paid Repurchase of Melrose Bancorp, Inc. common stock Shares repurchased for tax withholdings on stock-based compensation Stock options exercised Net cash provided by financing activities Net (decrease) increase in cash and cash equivalents Cash and cash equivalents at beginning of the year Cash and cash equivalents at end of the year Supplemental disclosures: Interest paid Income taxes paid Reclassification adjustment for stranded accumulated other comprehensive income due to tax rate change Organization, Consolidation and Presentation of Financial Statements [Abstract] NATURE OF OPERATIONS Accounting Policies [Abstract] SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Banking and Thrift [Abstract] Interest-Bearing Time Deposits with Other Banks Investments, Debt and Equity Securities [Abstract] INVESTMENTS IN AVAILABLE-FOR-SALE SECURITIES Debt Disclosure [Abstract] LOANS Property, Plant and Equipment [Abstract] PREMISES AND EQUIPMENT DEPOSITS Federal Home Loan Bank Advances [Abstract] Federal Home Loan Bank Advances Income Tax Disclosure [Abstract] Income Taxes Borrowed Funds Textual [Abstract] Benefit Plans Investments, All Other Investments [Abstract] FINANCIAL INSTRUMENTS Fair Value Disclosures [Abstract] FAIR VALUE MEASUREMENTS Other Comprehensive Loss [Abstract] OTHER COMPREHENSIVE LOSS Regulatory Matters [Abstract] REGULATORY MATTERS Equity [Abstract] COMMON STOCK REPURCHASES Related Party Transactions [Abstract] RELATED PARTY TRANSACTIONS Risks and Uncertainties [Abstract] SIGNIFICANT GROUP CONCENTRATIONS OF CREDIT RISK Subsequent Events [Abstract] SUBSEQUENT EVENTS Condensed Financial Information Disclosure [Abstract] CONDENSED PARENT COMPANY ONLY FINANCIAL STATEMENTS Quarterly Financial Information Disclosure [Abstract] QUARTERLY DATA (UNAUDITED) BASIS OF PRESENTATION USE OF ESTIMATES SIGNIFICANT GROUP CONCENTRATIONS OF CREDIT RISK CASH AND CASH EQUIVALENTS INTEREST-BEARING TIME DEPOSITS WITH OTHER BANKS SECURITIES FEDERAL HOME LOAN BANK STOCK LOANS ALLOWANCE FOR LOAN LOSSES PREMISES AND EQUIPMENT BANK-OWNED LIFE INSURANCE ADVERTISING INCOME TAXES EMPLOYEE STOCK OWNERSHIP PLAN STOCK-BASED COMPENSATION EARNINGS PER SHARE (EPS) FAIR VALUES OF FINANCIAL INSTRUMENTS RECENT ACCOUNTING PRONOUNCEMENTS Schedule of calculation of basic and diluted EPS Schedule of time deposits with other banks Schedule of amortized cost basis of securities and their approximate fair values Schedule maturities of debt securities Schedule of aggregate fair value and unrealized losses of securities that have been in a continuous unrealized loss position Schedule of loans Schedule of loans and allowance for loan losses Schedule of information regarding nonaccrual loans and past-due loans Schedule of premises and equipment Schedule of maturities Schedule of maturities of advances from the FHLB Schedule of FHLB borrowings Schedule of components of income tax expense Schedule of differences between the statutory federal income tax rates and the effective tax rates Schedule of deferred tax assets and gross deferred tax liabilities Capital One Schedule of principal balance on ESOP Debt Schedule of shares held by ESOP Schedule of financial instrument liabilities with off-balance sheet credit risk Schedule of assets measured at fair value on a recurring basis Schedule of financial instruments held or issued for purposes other than trading Schedule of components of other comprehensive loss included in stockholders' equity Schedule of bank's actual capital amounts and ratios Schedule of common stock repurchases Schedule of balance sheets Schedule of statements of income Schedule of statements of cash flows Schedule of quarterly financial information Melrose Cooperative Bank Foundation Melrose Cooperative Bank Nature Of Operations (Textual) Aggregate issuance of common stock shares Common stock , price per share Net proceeds from the stock offering Stock offering costs Cash funded to charitable foundation Expenses recognized Shares purchased under employee stock ownership plan Common stock, shares sold Basic Common Shares: Weighted average common shares outstanding Weighted average shares - unearned restricted stock Weighted average unallocated ESOP shares Basic weighted average shares outstanding Dilutive effect of unvested restricted stock awards Dilutive effect of stock options Diluted weighted average shares outstanding Basic earnings per share Diluted earnings per share Earnings Per Share [Abstract] Anti-dilutive securities excluded from computation of diluted earnings Significant Accounting Policies [Table] Significant Accounting Policies [Line Items] Furniture and equipment [Member] Buildings [Member] Summary of Significant Accounting Policies (Textual) Estimated useful lives Percentage of loan-to-value ratio Company tax rate Interest-bearing time deposits Reclassified from accumulated other comprehensive income to retained earnings Interest-Bearing Time Deposits with Other Banks (Textual) Due in one year or less Due in one year through three years Due in three years through five years Total time deposits Schedule of Available-for-sale Securities [Table] Debt Securities, Available-for-sale [Line Items] United States And Political Subdivisions [Member] Amortized Cost Basis Gross Unrealized Gains Gross Unrealized Losses Fair Value Fair Value Due within one year Due after one year through five years Due after five years through ten years Due after ten years Asset-backed securities Mortgage-backed securities Total Less than 12 Months, Fair Value Less than 12 Months, Unrealized Losses 12 Months or Longer, Fair Value 12 Months or Longer, Unrealized Losses Total, Fair Value Total, Unrealized Losses Amortized Cost and Fair Value Debt Securities [Abstract] Investments in Available for Sale Securities (Textual) Preferred stock, no stated maturity Number of securities with aggregate carrying amount exceeded 10% of stockholders' equity Gross realized gains on sales of available-for-sale securities Tax expense applicable to net realized gain Realized losses on available for sale securities Pledged securities Unrealized losses Unrealized losses, securities Percentage of unrealized losses of debt securities with amortized cost Unrealized losses Description of unrealized losses and federal agency obligation Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts, Notes, Loans and Financing Receivable [Line Items] Construction [Member] One-to four-family residential [Member] Home equity loans and lines of credit [Member] Commercial [Member] Consumer loans [Member] Total loans Allowance for loan losses Deferred loan costs, net Unamortized premiums Net loans Schedule Of Allowance For Loan Losses [Table] Schedule Of Allowance For Loan Losses [Line Items] One- to four- family Residential [Member] Consumer Loans [Member] Home Equity Loans and Lines of Credit [Member] Unallocated [Member] Beginning balance Charge offs Recoveries (Benefit)/provision Ending balance Individually evaluated for impairment Collectively evaluated for impairment Total allowance for loan losses ending balance Individually evaluated for impairment Collectively evaluated for impairment Total loans ending balance Schedule of Financing Receivables Past Due [Table] Financing Receivable, Recorded Investment, Past Due [Line Items] 90 Days or More Past Due [Member] 30 to 59 Days Past Due [Member] 60 to 89 Days Past Due [Member] Total Past Due Total Current Total 90 Days or More Past Due and Accruing Non-Accrual Receivables Acquired with Deteriorated Credit Quality [Member] One-to-Four-Family Residential Real Estate Loans [Member] One- to Four-Family Residential Loan [Member] Risk Rating 6 W - Pass Watch [Member] Risk Rate 7 [Member] Loans (Textual) Number of Impaired loan Impaired loan Troubled debt restructured, Number of loan Troubled debt restructured loan Amount of consumer mortgage loan in foreclosure process Number of consumer mortgage loans in foreclosure process Total balance Credit quality information requirement description Number of loans Property, Plant and Equipment [Table] Property, Plant and Equipment [Line Items] Building and improvements [Member] Construction in process [Member] Data processing equipment [Member] Premises and equipment, gross Accumulated depreciation 2019 2020 2021 2022 2023 Total FDIC insurance limit Aggregate amount of time deposit 2019 2020 2021 Total Schedule of Federal Home Loan Bank Advances, by Branch of FHLB Bank [Table] Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items] Co-Operative Central Bank [Member] Federal Home Loan Bank Advances (Textual) Purchase of additional FHLB stock FHLB Borrowings Maximum borrowing capacity Federal home loan bank, description Weighted-average interest rate on FHLB Interest rates on FHLB advances Current: Federal State Current Income Tax Expense (Benefit) Deferred: Federal Change in federal tax rate State Change in valuation allowance Deferred Income Tax Expense (Benefit) Total income tax expense Federal income tax at statutory rate State tax, net of federal tax benefit Change in valuation allowance Change in tax rate Dividends received deduction Bank-owned life insurance Credits Stock compensation Tax exempt income ESOP Other Effective tax rates Deferred tax assets: Allowance for loan losses Deferred compensation Security writedowns ESOP Stock based compensation Accrued expenses Contribution to Melrose Cooperative Bank Foundation Net unrealized holding loss on available-for-sale securities Gross deferred tax assets Valuation allowance Gross deferred tax assets, net of valuation allowance Deferred tax liabilities: Accelerated depreciation Prepaid expenses Net unrealized holding gain on available-for-sale securities Gross deferred tax liabilities Net deferred tax asset Income Taxes (Textual) Contribution to Melrose Cooperative Bank Foundation Gross deferred tax asset Valuation allowance against deferred tax assets Income tax charitable contribution carry forward Liability for uncertain tax positions Deferred tax assets tax expense Corporate income tax rate, description Federal income tax rate, description Compensation and Retirement Disclosure (Textual) 2019 2020 2021 2022 2023 Thereafter Loans receivable ESOP Unearned Compensation Restricted Stock Compensation and Retirement Disclosure [Abstract] Allocated Unallocated Shares held by ESOP Employer's expense under 401(k) plan Employees contribution to benefit plan Matching contribution by employer Liability for retirement benefit plans Employee vesting period Expense recognized for benefit plan Common stock purchased by ESOP Common stock purchased by ESOP, per share Percentage of aggregate purchase price of common stock Loan repayment period Defined contribution plan, vesting percentage per year Compensation expense recognized Fair value of unallocated ESOP shares Number of shares authorized under plan Number of shares awarded Weighted-average grant-date fair values of options granted per share Award vesting period Minimum vesting period from date of grant Stock-based compensation expense Stock-based compensation expense, related tax benefits Number of shares granted Stock options granted, exercise price Weighted average remaining years to vest Expected volatility Stock options granted, fair value Expected option life Period of U.S. Treasury rate Annual risk free interest rate Estimated fair value of award determined by Black-Scholes option pricing model Aggregate intrinsic value Stock option expense Options forfeited Number of unvested restricted stock awarded Unrecognized share based compensation expense Unrecognized compensation costs, weighted-average recognition period Number of shares outstanding Number of shares exercisable Weighted average remaining contractual terms, exercisable Unrecognized compensation costs Stock options exercised Number of shares held by the ESOP Schedule of Fair Value, Off-balance Sheet Risks [Table] Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items] Commitments to originate loans [Member] Unused lines of credit [Member] Due to borrowers on unadvanced construction loans [Member] Financial instrument liabilities with off-balance sheet credit risk Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value Hierarchy and NAV [Axis] Level 1 [Member] Level 2 [Member] Level 3 [Member] U.S. Government and Federal Agency Obligations [Member] Debt Securities Issued by States of the United States and Political Subdivisions of the States [Member] Corporate Bonds and Notes [Member] Asset-backed securities [Member] Mortgage-backed Securities [Member] Marketable Equity Securities [Member] Fair value on a recurring basis Fair Value, by Balance Sheet Grouping [Table] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Carrying Amount [Member] Financial assets: Cash and cash equivalents Available-for-sale securities Federal Home Loan Bank stock Loans, net Financial liabilities: Deposits FHLB advances Net unrealized holding (loss)/gain on available-for-sale securities Reclassification adjustment for net realized gains included in net income Other comprehensive loss before income tax effect Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Line Items] Other Comprehensive Loss (Textual) Reclassification adjustment for net realized gains in net income Tax benefit, included in income tax expense Total Capital (to Risk Weighted Assets), Actual Amount Tier 1 Capital (to Risk Weighted Assets), Actual Amount Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Amount Tier 1 Capital (to Average Assets), Actual Amount Total Capital (to Risk Weighted Assets), Actual Ratio Tier 1 Capital (to Risk Weighted Assets), Actual Ratio Common Equity Tier 1 Capital (to Risk Weighted Assets), Actual Ratio Tier 1 Capital (to Average Assets), Actual Ratio Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes, Amount Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes, Amount Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes, Amount Tier 1 Capital (to Average Assets), For Capital Adequacy Purposes, Amount Total Capital (to Risk Weighted Assets), For Capital Adequacy Purposes, Ratio Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purposes, Ratio Common Equity Tier 1 Capital (to Risk Weighted Assets), For Capital Adequacy Purpose, Ratio Tier 1 Capital (to Average Assets), For Capital Adequacy Purpose, Ratio Total Capital (to Risk Weighted Assets), Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Tier 1 Capital (to Risk Weighted Assets), Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Common Equity Tier 1 Capital (to Risk Weighted Assets), Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Tier 1 Capital (to Average Assets), Be Well Capitalized Under Prompt Corrective Action Provisions, Amount Total Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Common Equity Tier 1 Capital (to Risk Weighted Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Tier 1 Capital (to Average Assets), To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations [Table] Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items] Capital regulations [Member] Regulatory Matters (Textual) Common equity tier 1 capital ratio Minimum tier 1 capital to risk-weighted assets ratio Total capital to risk weighted assets, minimum capital requirement ratio Tier 1 leverage ratio, minimum capital requirement ratio Common equity tier 1 capital, minimum to be well capitalized ratio Tier 1 capital to risk weighted assets, minimum to be well capitalized ratio Total capital to risk weighted assets, minimum to be well capitalized ratio Phase in period term Tier 1 capital to risk-weighted assets capital conservation buffer above the required capital ratios Annual Increase Tier 1 leverage ratio, minimum to be well capitalized ratio Tier 1 capital to risk-weighted assets capital conservation buffer above the required capital ratios that began phasing in January 1, 2016 Tier 1 capital to risk-weighted assets capital conservation buffer above the required capital ratios annual fully phased in effective January 1, 2019 Regulatory requirements capital ratios, description Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] January 1, 2018 to January 31, 2018 [Member] February 1, 2018 through February 28, 2018 [Member] March 1, 2018 through March 31, 2018 [Member] April 1, 2018 to April 30, 2018 [Member] May 1, 2018 to May 31, 2018 [Member] June 1, 2018 to June 30, 2018 [Member] July 1, 2018 to July 31, 2018 [Member] August 1, 2018 to August 31, 2018 [Member] September 1, 2018 to September 30, 2018 [Member] October 1, 2018 to October 31, 2018 [Member] November 1, 2018 to November 30, 2018 [Member] December 1, 2018 to December 31, 2018 [Member] Total Number of Shares Purchased Average Price Paid Per Share Total Number of Shares Purchased as Part of Publicly Announced Plans or Programs Maximum Number of Shares that May Yet Be Purchased Under the Plans or Programs Common Stock Repurchases (Textual) Number of shares authorized to be repurchased Additional number of shares authorized for repurchase Additional number of shares authorized for repurchase, percentage Remaining number of shares authorized to be repurchased Repurchased shares of common stock Related Party Transactions (Textual) Loans amount New loan disbursements Advances amount Principal payments totaled Loan payoffs totaled Deposits from related parties Subsequent Event [Table] Subsequent Event [Line Items] Subsequent Events (Textual) Common stock dividend declared, cash Dividend payable declared date Dividend payable recorded date Subsequent event, description Repurchased shares of common stock Common stock average cost Repurchased value Assets Non-interest bearing deposit in the Bank Cash and cash equivalents Interest-bearing time deposits with other banks Investments in available-for-sale securities (at fair value) Investment in subsidiary, Melrose Bank Loan receivable ESOP Deferred tax assets Total assets Liabilities and Stockholders' Equity Stockholders' equity Total liabilities and stockholders' equity Interest on cash and cash equivalents Interest on ESOP loan Interest and dividends on securities Total interest and dividend income Loss on available-for-sale securities Total noninterest expense Loss before undistributed income of subsidiary and income tax expense (benefit)/expense Undistributed income of subsidiary Income before income taxes Income tax (benefit) expense Loss on available-for-sale securities Increase in accrued interest receivable Decrease in other liabilities Stock based compensation expense Equity in undistributed earnings of subsidiary Net cash provided by operating activities Cash flows from investing activities: Purchases of interest-bearing time deposits with other banks Proceeds from maturities of available-for-sale securities Repayment of principal on ESOP loan Net cash provided by (used in) investing activities Cash flows from financing activities: Payment of income taxes for shares withheld in stock based award activity Cash paid for stock repurchases Dividend paid Net cash used in financing activities Net decrease in cash and cash equivalents Interest and dividend income Interest expense Net interest and dividend income Provision/(benefit) for loan losses Net interest and dividend income, after provision/(benefit) for loan losses Total noninterest income Provision for income taxes Amortized Cost and Fair Value Debt Securities [Abstract] Noninterest expense associated with audits and examinations. Available for sale securities debt asset backed securities. Available for sale securities debt mortgage backed securities. Available for sale securities income tax expense on realized gains. Bank Owned Life Insurance Policy. Capital Regulations [Member] Capital Required For Capital Adequacy To Risk Weighted Asset Amount of change in unamortized premiums. Common Equity Tier One Capital Required For Capital Adequacy To Risk Weighted Assets Common Equity Tier One Capital Required To Be Well Capitalized To Risk Weighted Assets Consumer mortgage loans in process of foreclosure. Common stock held by ESOP committed to be allocated shares. Common stock held by ESOP committed to be allocated value. Construction portfolio segment. Consumer mortgage loans in process of foreclosure. Cooperative central bank. Data Processing Equipment [Member] Deferred tax assets employee stock ownership plan. Deferred tax assets unrealized loss on available for sales securities. Deferred tax liabilities unrealized gain on available for sales securities. Dilutive effect stock options. Document And Entity Information [Abstract] Effective Income Tax Rate Reconciliation, Employee Stock Ownership Plan. Employee stock ownership plan loans receivable due in five fiscal years thereafter. Employee stock ownership plan loans receivable due in next twelve months. Employee stock ownership plan loans receivable due in year five. Employee stock ownership plan loans receivable due in year four. Employee stock ownership plan loans receivable due in year three. Employee stock ownership plan loans receivable due in year two. ESOP loan receivable. Federal Home Loan Bank Stock Policy Text Block. Financing Receivable Modifications Number Of Loans Home equity loans and lines of credit portfolio segment. Impaired Financing Receivable Number Of Loans Amount of increase decrease in demand deposits and savings for the reporting period. Investments in available for sale securities textual. Loans and leases receivable unamortized premiums. Loans receivables related risk rating seven. Loans receivables related risk rating six. Marketable Equity Securities. Minimum vesting period from date of grant. New Base Three Requirement Phased In Time Frame Period Number of consumer mortgage loans in foreclosure process. Number of family residential mortgage loans. One Four Family Residential Loans [Member] One to four family residential real estate loans. Unrealized loss as a percentage of amortized cost. Period of U.S. Treasury rate. Net Loan activity for the period. Loan originations and principal advances net principal collections. Provision benefit for loan and lease losses. Schedule Of Allowance For Loan Losses [Line Items] Schedule Of Allowance For Loan Losses [Table] Tabular disclosure of advances borrowings made and reported by Federal Home Loan Bank (FHLBank). Share based compensation arrangement by share based payment award fair value assumptions estimated fair value. Share repurchase program additional number of shares authorized To be repurchased. Significant Accounting Policies [Line Items] Significant Accounting Policies [Table] Number of shares repurchased for tax withholdings on stock-based compensation. Stock issued during period restricted stock award expense. Stock repurchase program additional number of shares authorized to be repurchased as percentage of issued and outstanding shares. Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock. Tax cuts and Jobs act of 2017 change in Tax rate revaluation of deferred tax assets Income tax expense benefit. Tier one risk based capital to risk weighted assets capital conservation buffer above required capital ratios. Tier one risk based capital to risk weighted assets capital conservation buffer above required capital ratios annual increases. Tier one risk based capital to risk weighted assets capital conservation buffer above required capital ratios fully phased amount. The total amount of time deposits. Amount of time deposits maturing in the fifth fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Amount of time deposits maturing in the next fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Amount of time deposits maturing in the third fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. Two thousand and fifteen equity incentive plan. Unearned compensation restricted stock. Unearned compensation restricted stock. Employee stock ownership plan ESOP percentage of aggregate purchase price of common stocks. Employee stock ownership plan ESOP loan repayment period. Employee stock ownership plan fair value of unallocated shares. Related party transactions loan payoffs totaled. Advances amount. Common stock average cost. Interest On ESOP Loan Receivable Loss on available-for-sale securities. Interest on cash and cash equivalents. Repayment of loans from employee stock option plan. Cash and Cash Equivalents, at Carrying Value Deposits [Default Label] Liabilities Unearned ESOP Shares Unearned Compensation Restricted Stock [Default Label] Interest Income (Expense), after Provision for Loan Loss Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent Comprehensive Income (Loss), Net of Tax, Attributable to Parent Shares, Outstanding Dividends Stock Repurchased During Period, Shares Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition Accretion (Amortization) of Discounts and Premiums, Investments Provision Benefit for Loan and Lease Losses Amortization of Deferred Loan Origination Fees, Net Increase (Decrease) in Accrued Interest Receivable, Net Increase (Decrease) in Other Operating Assets Payments to Acquire Available-for-sale Securities Payments to Acquire Federal Home Loan Bank Stock Proceeds Payments Of Loan Originations And Principal Collection Net Payments to Acquire Loans Held-for-investment Payments to Acquire Property, Plant, and Equipment Payment to Acquire Life Insurance Policy, Investing Activities Payments for FHLBank Advance, Investing Activities Payments of Dividends Payments for Repurchase of Common Stock Payments Related to Tax Withholding for Share-based Compensation Proceeds from Stock Options Exercised Concentration Risk, Credit Risk, Policy [Policy Text Block] Finance, Loans and Leases Receivable, Policy [Policy Text Block] Property, Plant and Equipment, Policy [Policy Text Block] Weighted Average Number of Shares, Restricted Stock Weighted Average Number of Shares, Employee Stock Ownership Plan Shares Not Committed to be Released Tier One Risk Based Capital To Risk Weighted Assets Capital Conservation Buffer Above Required Capital Ratios Available-for-sale Equity Securities, Accumulated Gross Unrealized Loss, before Tax Allowance for Loan and Lease Losses, Write-offs Financing Receivable, Individually Evaluated for Impairment Financing Receivable, Collectively Evaluated for Impairment Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment Time Deposits Federal Home Loan Bank, Advances, Maturities Summary, Due in Next Twelve Months Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Two Federal Home Loan Bank, Advances, Maturities Summary, Due in Year Three Advances from Federal Home Loan Banks Federal Home Loan Bank, Advances, Branch of FHLB Bank, Interest Rate Federal Home Loan Bank, Advances, Interest Rate Current Income Tax Expense (Benefit) Deferred Federal Income Tax Expense (Benefit) Deferred State and Local Income Tax Expense (Benefit) Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount Effective Income Tax Rate Reconciliation, Deduction, Dividend, Percent Effective Income Tax Rate Reconciliation, Nondeductible Expense, Life Insurance, Percent Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Allowance for Doubtful Accounts Financing Receivable Modifications Number Of Loans Deferred Tax Assets, Gross Deferred Tax Liabilities, Property, Plant and Equipment Deferred Tax Liabilities, Prepaid Expenses Impaired Financing Receivable Number Of Loans Deferred Tax Liabilities, Gross CorporateIncomeTaxRateDescription FederalIncomeTaxRate Loans Receivables Related Risk Rating Seven [Member] [Default Label] Minimum Vesting Period From Date Of Grant Marketable Equity Securities [Member] Loans Textual [Abstract] Loans Receivables Related Risk Rating Six [Member] [Default Label] Allocated Share-based Compensation Expense Stock or Unit Option Plan Expense Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures Repayment of Loans From Employee Stock Option Plan Provision for Loan Losses Expensed