Document And Entity Information Statistical Measurement [Axis] Note To Financial Statement Details Textual Document Fiscal Period Focus EBP, Note Receivable from Participant [Policy Text Block] Significant Accounting Policies Document Fiscal Year Focus Note 1 - Description of Plan wsbf_EBPVestingPercentageTrancheTwo Vesting percentage Vesting percentage in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), tranche two. Note 3 - Fair Value Measurements Net assets available for benefits wsbf_EBPVestingPercentageTrancheThree Vesting percentage Vesting percentage in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), tranche three, Schedule H , Line 4i Amendment Flag wsbf_EBPVestingYearOfServiceTrancheThree Vesting years of service (Year) Number of vesting years of service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), tranche three, Note 1- Description of Plan - Summary of Vesting Schedule (Details) wsbf_EBPVestingPercentageTrancheOne Vesting percentage Vesting percentage in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), tranche one. Note 3 - Fair Value Measurements - EBP, Investment, Fair Value and NAV (Details) Schedule H, Line 4i - Schedule of Assets (Held at End of Year) 2 (Details) Schedule H, Line 4i - Schedule of Assets (Held at End of Year) 2 2 (Details) Notes To Financial Statements Minimum [Member] Notes To Financial Statements [Abstract] dei_DocumentPeriodEndDate Document Period End Date Statistical Measurement [Domain] Maximum [Member] Legal Entity [Axis] us-gaap-ebp_EmployeeBenefitPlanParticipantLoanMaturityDate EBP, Asset Held for Investment, Participant Loan, Maturity Date Notes receivable from participants EBP, Investment, Fair Value and NAV [Text Block] Entity [Domain] Interest on notes receivable from participants EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Note Receivable from Participant Entity Central Index Key Appreciation in fair value of investments dei_EntityRegistrantName Entity Registrant Name wsbf_PolicyTable Entity Current Reporting Status EBP, Description of Plan [Text Block] EBP, Related Party and Party-in-Interest Transactions [Table] Current Fiscal Year End Date us-gaap-ebp_EmployeeBenefitPlanTaxDeterminationLetterDate EBP, Tax Determination Letter, Date EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncrease Total additions Entity Shell Company us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseForParticipantContribution Total contributions Common Collective Trust [Member] Entity Emerging Growth Company Entity Small Business Investments [Domain] EBP, Employer, Common Stock [Member] Benefits paid to participants Accounting Policies [Abstract] Rollovers Employer us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecreaseForIncomeLossOnInvestment Total investment gain Valuation Approach and Technique [Domain] us-gaap-ebp_EmployeeBenefitPlanTaxQualificationStatusExtensibleEnumeration EBP, Tax Qualification Status [Extensible Enumeration] Valuation, Market Approach [Member] Statement of Stockholders' Equity [Abstract] EBP, Tax Status [Text Block] us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccount EBP, Forfeited Nonvested Account us-gaap-ebp_EmployeeBenefitPlanInvestmentValuationTechniqueExtensibleEnumeration EBP, Investment, Valuation Technique [Extensible Enumeration] Investment, current value Equity Components [Axis] Investments – at fair value Class of Stock [Axis] Equity Component [Domain] Fair Value, Inputs, Level 2 [Member] Fair Value, Inputs, Level 3 [Member] Fair Value, Inputs, Level 1 [Member] us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitIncreaseDecrease Total net increase Deductions from net assets attributed to: us-gaap-ebp_EmployeeBenefitPlanParticipantLoanInterestRate EBP, Asset Held for Investment, Participant Loan, Interest Rate us-gaap-ebp_EmployeeBenefitPlanForfeitedNonvestedAccountDecreaseForEmployerContribution EBP, Forfeited Nonvested Account, Decrease from Employer Contribution EBP, Participant-Directed [Member] Contributions Investment income: Interest and dividend income Investments, at fair value Administrative expenses Investment, Identifier [Axis] EBP, Accounting Policy [Table] Receivables EBP, Description of Plan [Table] Statement [Table] EBP, Tax Status [Table] Fair Value Hierarchy and NAV [Domain] Statement of Financial Position [Abstract] EBP, Participant-Directed and Nonparticipant-Directed Status [Domain] us-gaap-ebp_EmployeeBenefitPlanParticipantContributionAutomaticDeferralRate EBP, Participant Contribution, Automatic, Deferral Rate Investment Type [Axis] us-gaap-ebp_EmployeeBenefitPlanInvestmentNumberOfSharesPurchased EBP, Investment, Purchased, Number of Shares us-gaap-ebp_EmployeeBenefitPlanEmployerContributionMatchingPercentage EBP, Employer Contribution, Matching Percentage Mutual Fund [Member] EBP, Schedule of Asset Held for Investment [Text Block] us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingAmount EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMinimumBorrowingAmount EBP, Note Receivable from Participant, Account, Minimum Borrowing, Amount us-gaap-ebp_EmployeeBenefitPlanParticipantContributionPretaxMaximumAnnualCompensationToTotalCompensationPercentage EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage EBP, Related Party and Party-in-Interest [Domain] EBP, Subsequent Event [Policy Text Block] EBP, Investment, Issuer Name us-gaap-ebp_EmployeeBenefitPlanInvestmentNumberOfSharesSold EBP, Investment, Sold, Number of Shares dei_DocumentType Document Type EBP, Summary of Accounting Policy [Text Block] EBP, Investment, Excluding Plan Interest in Master Trust, Cost Document Information [Line Items] EBP, Investment [Policy Text Block] Document Information [Table] wsbf_EBPParticipantMaximumCatchupContributionIRSLimit EBP, Participant Maximum Catch-up Contribution, IRS Limit IRS limit of maximum amount of catch-up contribution that is permitted to contribute to employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). EBP, Trustee [Member] wsbf_EBPMinimumAgeOfParticipantToTakeInServiceDistribution EBP, Minimum Age of Participant to Take In Service Distribution Minimum age of participant required to take in service distribution in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). wsbf_EBPMinimumEligibleAgeOfParticipant EBP, Minimum Eligible Age of Participant Minimum eligible age of participant required in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Entity Interactive Data Current wsbf_EBPMinimumEligibleServiceTermOfParticipant EBP, Minimum Eligible Service Term of Participant Represent minimum eligible service term of participant required in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). Statement [Line Items] EBP 90-1026709 002 [Member] Represents EBP 90-1026709 002. Fair Value Hierarchy and NAV [Axis] EBP, Basis of Accounting and Use of Estimate [Policy Text Block] Disclosure of accounting policy for summary of accounting policy used to prepare financial statement of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) and use of estimate in preparation of financial statement of employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). EBP, Related Party and Party-in-Interest [Axis] EBP, Summary of Employer Contribution Vesting Schedule [Table Text Block] Tabular disclosure of vesting schedule of employer contribution in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). wsbf_EBPMaximumVestedAccountBalanceRequiredForParticipantToMakeDistribution EBP, Maximum Vested Account Balance Required for Participant to Make Distribution Maximum amount of plan asset, in vested account required for participant to make distribution in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). wsbf_EBPTerminationOfPlanVestedPercentage EBP, Termination of Plan, Vested Percentage Vesting percentage in accounts in case of employee benefit plan (EBP) plan termination. DWS [Member] Represents DWS. American Funds [Member] Represents American funds. us-gaap-ebp_EmployeeBenefitPlanAsset Total assets EBP, Payment to Participant [Policy Text Block] BlackRock Investments, LLC [Member] Represents BlackRock Investments, LLC. FlexPath Strategies [Member] Represents FlexPath Strategies. us-gaap-ebp_EmployeeBenefitPlanParticipantContributionPretaxMaximumAnnualCompensationAmount EBP, Participant Contribution, Pretax, Maximum Annual Compensation, Amount us-gaap-ebp_EmployeeBenefitPlanInvestmentSoldExcludingPlanInterestInMasterTrustSellingPrice EBP, Investment Sold, Excluding Plan Interest in Master Trust, Selling Price Schedule of Assets [Text Block] The entire disclosure for schedule of assets. us-gaap-ebp_EmployeeBenefitPlanNoteReceivableFromParticipantAccountMaximumBorrowingToTotalAccountPercentage EBP, Note Receivable from Participant, Account, Maximum Borrowing, to Total Account, Percentage us-gaap-ebp_EmployeeBenefitPlanEmployerContributionParticipantCompensationMatchedPercentage EBP, Employer Contribution, Participant Compensation Matched, Percentage wsbf_EBPInvestmentLevel3ReconciliationIncreaseDecreaseFromTransferIntoOrOutOfLevel3 EBP, Investment, Level 3 Reconciliation, Increase (Decrease) from Transfer into or Out of Level 3 Amount of increase or decrease in investment, measured using unobservable input, held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)) from transfer into or out of Level 3 of fair value hierarchy . Investment, Issuer Name [Domain] Waterstone Financial [Member] Represents Waterstone Financial. us-gaap-ebp_EmployeeBenefitPlanTaxDeterminationLetterObtained EBP, Tax Determination Letter, Obtained [true false] EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status JP Morgan [Member] Represents JP Morgan. us-gaap-ebp_EmployeeBenefitPlanChangeInNetAssetAvailableForBenefitDecrease Total deductions PIMCO [Member] Represents PIMCO. Franklin [Member] Represents Franklin. EBP, Related Party and Party-in-Interest Transactions [Text Block] John Hancock [Member] Represents John Hancock. Assets DFA [Member] Represents DFA. us-gaap-ebp_EmployeeBenefitPlanNetAssetAvailableForBenefit Net asset available for benefits Beginning of year End of year Fidelity [Member] Represents Fidelity. wsbf_EBPVestingYearOfServiceTrancheOne Vesting years of service (Year) Number of vesting years of service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), tranche one. us-gaap-ebp_EmployeeBenefitPlanInvestmentAcquiredExcludingPlanInterestInMasterTrustCost EBP, Investment Acquired, Excluding Plan Interest in Master Trust, Cost wsbf_EBPVestingYearOfServiceTrancheTwo Vesting years of service (Year) Number of vesting years of service in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), tranche two. EBP, Investment, Fair Value and NAV [Table Text Block] us-gaap_PolicyTextBlockAbstract Accounting Policies Participants' EBP, Investment, Fair Value and NAV [Table] us-gaap_DisclosureTextBlockAbstract Notes to Financial Statements Retirement Plan Tax Status [Domain] us-gaap_TableTextBlock Notes Tables Qualified Plan [Member]