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Interest-bearing checking sfbs_DebtSecuritiesHeldtomaturityContinuousUnrealizedLossPosition12MonthsOrLongerAccumulatedLoss1 Debt securities held to maturity, more than twelve months, gross unrealized losses Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for 12 months or longer. sfbs_DebtSecuritiesHeldtomaturityContinuousUnrealizedLossPositionLessThan12MonthsFairValue1 Debt securities held to maturity, less than twelve months, fair value Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for less than 12 months. sfbs_DebtSecuritiesHeldtomaturityUnrealizedLossPositionAccumulatedLoss1 Debt securities held to maturity, gross unrealized losses Total Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position. sfbs_DebtSecuritiesHeldtomaturityContinuousUnrealizedLossPosition12MonthsOrLongerFairValue1 Debt securities held to maturity, more than twelve months, fair value Fair value of investment in debt security measured at amortized cost (held-to-maturity), in continuous unrealized loss position for 12 months or longer. dei_EntityFilerCategory Entity Filer Category dei_EntityShellCompany Entity Shell Company dei_EntityEmergingGrowthCompany Entity Emerging Growth Company us-gaap_OtherComprehensiveIncomeLossNetOfTax Other comprehensive income (loss), net of tax Loss on sale of debt securities available for sale sfbs_DebtSecuritiesHeldtomaturityContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss1 Debt securities held to maturity, less than twelve months, gross unrealized losses Amount of accumulated unrealized loss on investment in debt security measured at amortized cost (held-to-maturity), in continuous loss position for less than 12 months. Nonperforming Financial Instruments [Member] dei_EntitySmallBusiness Entity Small Business sfbs_DebtSecuritiesHeldtomaturityUnrealizedLossPositionFairValue1 Debt securities held to maturity, fair value Fair value of investment in debt security measured at amortized cost (held-to-maturity), in unrealized loss position. Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Dividends on preferred stock Interest expense: Borrowed funds Interest-bearing balances due from depository institutions Derivative Instruments and Hedging Activities Disclosure [Text Block] us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Nonvested, Number of Shares Debt securities Deposits Entity Address, State or Province Entity Address, City or Town Marketable Securities [Table] Retained earnings us-gaap_InterestExpenseOperating Total interest expense Entity Address, Address Line One Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] dei_CityAreaCode City Area Code us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet Net change in other assets, liabilities, and other operating activities Due from one to five years, amortized cost us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation Taxes paid in net settlement of tax obligation upon exercise of stock options Due from five to ten years, amortized cost us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost dei_LocalPhoneNumber Local Phone Number Due within one year, amortized cost us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost Entity Address, Postal Zip Code Other borrowings Derivative [Table] Preferred Stock [Member] Mortgage-backed securities, fair value us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue Title of 12(b) Security Cash and Cash Equivalents Disclosure [Text Block] Security Exchange Name Due from five to ten years, fair value us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue Trading Symbol Due after ten years, fair value us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue Due within one year, fair value us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue Due from one to five years, fair value us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue Due after ten years, amortized cost us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost Mortgage-backed securities, amortized cost us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost Class of Stock [Axis] Class of Financing Receivable [Axis] Class of Financing Receivable [Domain] Entity Common Stock, Shares Outstanding (in shares) Other comprehensive (loss) income, net of tax Earnings Per Share [Text Block] OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax Unrealized net holding gains (losses) arising during period from debt securities available for sale, net of tax of $90 and $858 for the three months ended June 30, 2026 and 2025, respectively, and $(178) and $3,262 for the six months ended June 30, 2026 and 2025, respectively Internal Credit Assessment [Axis] us-gaap_AvailableforsaleSecuritiesSoldAtPar Debt Securities, Available-for-Sale, Sold at Par Value Held to maturity debt securities, fair value Debt Securities, Held-to-Maturity, Fair Value Held to maturity debt securities, fair value us-gaap_InterestIncomeExpenseAfterProvisionForLoanLoss Net interest income after provision for credit losses Exercisable, aggregate intrinsic value us-gaap_InterestIncomeFederalFundsSold Federal funds sold and securities purchased with agreement to resell Internal Credit Assessment [Domain] Common Stock, Par or Stated Value Per Share (in dollars per share) Additional performance share attainment, weighted average grant date fair value (in dollars per share) The weighted average fair value at grant date for nonvested additional performance share attainment during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). Held to maturity debt securities, Due within one year, fair value us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue Held to maturity debt securities, Due from one to five years, fair value us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue Other liabilities Additional performance share attainment, shares (in shares) The number of additional performance shares attained during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). sfbs_PaymentsProceedsOfOrdinaryDividendsCommonStock Dividends paid on common stock The amount of cash outflow (inflow) from ordinary dividends of common stock. Mortgage-backed securities, fair value us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax Cash and due from banks Cash and due from banks us-gaap_Assets Total assets us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax Net losses on sales of debt securities, net of tax of $2,150 and $2,150 for the three and six months ended June 30, 2025, respectively Other interest and dividends Non-owner Occupied Commercial [Member] Represents the Non-owner occupied commercial real-estate. Modifications, amount Modifications, percentage of total loans Diluted earnings per common share (in dollars per share) srt_MortgageLoansOnRealEstateNumberOfLoans SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate, Number of Loans Time Deposit Maturities [Table Text Block] us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation Shares of common stock withheld in net settlement upon exercise of stock options Amortization of investments in tax credit partnerships Amount of amortization of investments in tax credit partnerships. us-gaap_OtherShortTermBorrowings Other borrowings sfbs_OtherRealEstateAndRepossessedAssetsFairValue Other real estate owned and repossessed assets Represents fair value of other real estate and repossessed assets. sfbs_DebtSecuritiesHeldtoMaturityExcludingAccruedInterestBeforeAllowanceForCreditLoss1 Held to maturity debt securities Amount excluding accrued interest, before allowance for credit loss, of investment in debt security measured at amortized cost (held-to-maturity). Accounts and Financing Receivables [Table] Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] us-gaap_RevenueNotFromContractWithCustomerExcludingInterestIncome Revenue not from contract with customer Interest us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest Comprehensive income us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest Total stockholders' equity Balance Balance us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff Financing Receivable, Originated, More than Five Years before Current Fiscal Year, Writeoff us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff Financing Receivable, Revolving, Writeoff us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff Financing Receivable, Year Four, Originated, Three Years before Current Fiscal Year, Writeoff us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff Financing Receivable, Year Five, Originated, Four Years before Current Fiscal Year, Writeoff us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff Financing Receivable, Year Two, Originated, Fiscal Year before Current Fiscal Year, Writeoff us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff Financing Receivable, Year Three, Originated, Two Years before Current Fiscal Year, Writeoff us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff Financing Receivable, Year One, Originated, Current Fiscal Year, Writeoff us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff Financing Receivable, Revolving, Converted to Term Loan, Writeoff Noncontrolling Interest [Member] New Adopted Accounting Pronouncements [Text Block] The entire disclosure for new adopted accounting pronouncements. us-gaap_StockholdersEquity Total stockholders' equity attributable to ServisFirst Bancshares, Inc. Forfeited, weighted average grant date fair value (in dollars per share) us-gaap_OciDebtSecuritiesAvailableForSaleTransferToHeldToMaturityAdjustmentFromAociForAmortizationOfGainLossAfterTax Amortization of net unrealized gains on debt securities transferred from available-for-sale to held-to-maturity, net of tax of $(27) and $(40) for the three months ended June 30, 2026 and 2025, respectively, and $(55) and $(75) for the six months ended June 30, 2026 and 2025, respectively us-gaap_PaymentsForOriginationOfMortgageLoansHeldForSale Originations of mortgage loans held for sale OCI, Debt Securities, Available-for-Sale, Transfer to Held-to-Maturity, Adjustment from AOCI for Amortization of Gain (Loss), Tax Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block] us-gaap_OperatingLeaseRightOfUseAsset Operating Lease, Right-of-Use Asset Dividends paid on preferred stock Credit Card [Member] ecd_Rule10b51ArrTrmntdFlag Rule 10b5-1 Arrangement Terminated [Flag] ecd_Rule10b51ArrAdoptedFlag Rule 10b5-1 Arrangement Adopted [Flag] Term Extensions (Month) Represents the term extension for modified financing receivables. Total Payment Deferral Represents the value of deferred payments for modification of financing receivables.