3.23.1 html 244 516 1 false 78 0 false 9 false false R1.htm 00090 - Document - Document and Entity Information Sheet http://www.johnmarshallbank.com/role/DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 00100 - Statement - Consolidated Balance Sheets Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedBalanceSheets Consolidated Balance Sheets Statements 2 false false R3.htm 00105 - Statement - Consolidated Balance Sheets (Parenthetical) Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedBalanceSheetsParenthetical Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 00200 - Statement - Consolidated Statements of Income Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedStatementsOfIncome Consolidated Statements of Income Statements 4 false false R5.htm 00300 - Statement - Consolidated Statements of Comprehensive Income Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedStatementsOfComprehensiveIncome Consolidated Statements of Comprehensive Income Statements 5 false false R6.htm 00305 - Statement - Consolidated Statements of Comprehensive Income (Parenthetical) Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedStatementsOfComprehensiveIncomeParenthetical Consolidated Statements of Comprehensive Income (Parenthetical) Statements 6 false false R7.htm 00400 - Statement - Consolidated Statements of Shareholders' Equity Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedStatementsOfShareholdersEquity Consolidated Statements of Shareholders' Equity Statements 7 false false R8.htm 00405 - Statement - Consolidated Statements of Shareholders' Equity (Parenthetical) Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedStatementsOfShareholdersEquityParenthetical Consolidated Statements of Shareholders' Equity (Parenthetical) Statements 8 false false R9.htm 00500 - Statement - Consolidated Statements of Cash Flows Sheet http://www.johnmarshallbank.com/role/StatementConsolidatedStatementsOfCashFlows Consolidated Statements of Cash Flows Statements 9 false false R10.htm 10101 - Disclosure - Nature of Business and Summary of Significant Accounting Policy Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicy Nature of Business and Summary of Significant Accounting Policy Notes 10 false false R11.htm 10201 - Disclosure - Investment Securities Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecurities Investment Securities Notes 11 false false R12.htm 10301 - Disclosure - Loans Sheet http://www.johnmarshallbank.com/role/DisclosureLoans Loans Notes 12 false false R13.htm 10401 - Disclosure - Allowance for Loan Losses Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLosses Allowance for Loan Losses Notes 13 false false R14.htm 10501 - Disclosure - Derivatives Sheet http://www.johnmarshallbank.com/role/DisclosureDerivatives Derivatives Notes 14 false false R15.htm 10601 - Disclosure - Bank Premises and Equipment, Net Sheet http://www.johnmarshallbank.com/role/DisclosureBankPremisesAndEquipmentNet Bank Premises and Equipment, Net Notes 15 false false R16.htm 10701 - Disclosure - Deposits and Borrowings Sheet http://www.johnmarshallbank.com/role/DisclosureDepositsAndBorrowings Deposits and Borrowings Notes 16 false false R17.htm 10801 - Disclosure - Leases Sheet http://www.johnmarshallbank.com/role/DisclosureLeases Leases Notes 17 false false R18.htm 10901 - Disclosure - Income Taxes Sheet http://www.johnmarshallbank.com/role/DisclosureIncomeTaxes Income Taxes Notes 18 false false R19.htm 11001 - Disclosure - Restriction on Cash Sheet http://www.johnmarshallbank.com/role/DisclosureRestrictionOnCash Restriction on Cash Notes 19 false false R20.htm 11101 - Disclosure - Commitments and Contingencies Sheet http://www.johnmarshallbank.com/role/DisclosureCommitmentsAndContingencies Commitments and Contingencies Notes 20 false false R21.htm 11201 - Disclosure - Fair Value Measurements Sheet http://www.johnmarshallbank.com/role/DisclosureFairValueMeasurements Fair Value Measurements Notes 21 false false R22.htm 11301 - Disclosure - Earnings per Common Share Sheet http://www.johnmarshallbank.com/role/DisclosureEarningsPerCommonShare Earnings per Common Share Notes 22 false false R23.htm 11401 - Disclosure - Stock Based Compensation Plan Sheet http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlan Stock Based Compensation Plan Notes 23 false false R24.htm 11501 - Disclosure - Employee Benefit Plans Sheet http://www.johnmarshallbank.com/role/DisclosureEmployeeBenefitPlans Employee Benefit Plans Notes 24 false false R25.htm 11601 - Disclosure - Regulatory Capital Sheet http://www.johnmarshallbank.com/role/DisclosureRegulatoryCapital Regulatory Capital Notes 25 false false R26.htm 11701 - Disclosure - Revenue Sheet http://www.johnmarshallbank.com/role/DisclosureRevenue Revenue Notes 26 false false R27.htm 11801 - Disclosure - Other Operating Expenses Sheet http://www.johnmarshallbank.com/role/DisclosureOtherOperatingExpenses Other Operating Expenses Notes 27 false false R28.htm 11901 - Disclosure - Low Income Housing Tax Credit Investments Sheet http://www.johnmarshallbank.com/role/DisclosureLowIncomeHousingTaxCreditInvestments Low Income Housing Tax Credit Investments Notes 28 false false R29.htm 12001 - Disclosure - Accumulated Other Comprehensive Income (Loss) Sheet http://www.johnmarshallbank.com/role/DisclosureAccumulatedOtherComprehensiveIncomeLoss Accumulated Other Comprehensive Income (Loss) Notes 29 false false R30.htm 12101 - Disclosure - Parent Company Financials Sheet http://www.johnmarshallbank.com/role/DisclosureParentCompanyFinancials Parent Company Financials Notes 30 false false R31.htm 12201 - Disclosure - Related Party Transactions Sheet http://www.johnmarshallbank.com/role/DisclosureRelatedPartyTransactions Related Party Transactions Notes 31 false false R32.htm 20102 - Disclosure - Nature of Business and Summary of Significant Accounting Policy (Policies) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyPolicies Nature of Business and Summary of Significant Accounting Policy (Policies) Policies http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicy 32 false false R33.htm 30203 - Disclosure - Investment Securities (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesTables Investment Securities (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureInvestmentSecurities 33 false false R34.htm 30303 - Disclosure - Loans (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureLoansTables Loans (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureLoans 34 false false R35.htm 30403 - Disclosure - Allowance for Loan Losses (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesTables Allowance for Loan Losses (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLosses 35 false false R36.htm 30503 - Disclosure - Derivatives (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureDerivativesTables Derivatives (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureDerivatives 36 false false R37.htm 30603 - Disclosure - Bank Premises and Equipment, Net (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureBankPremisesAndEquipmentNetTables Bank Premises and Equipment, Net (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureBankPremisesAndEquipmentNet 37 false false R38.htm 30703 - Disclosure - Deposits and Borrowings (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureDepositsAndBorrowingsTables Deposits and Borrowings (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureDepositsAndBorrowings 38 false false R39.htm 30803 - Disclosure - Leases (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesTables Leases (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureLeases 39 false false R40.htm 30903 - Disclosure - Income Taxes (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureIncomeTaxesTables Income Taxes (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureIncomeTaxes 40 false false R41.htm 31103 - Disclosure - Commitments and Contingencies (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureCommitmentsAndContingenciesTables Commitments and Contingencies (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureCommitmentsAndContingencies 41 false false R42.htm 31203 - Disclosure - Fair Value Measurements (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureFairValueMeasurementsTables Fair Value Measurements (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureFairValueMeasurements 42 false false R43.htm 31303 - Disclosure - Earnings per Common Share (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureEarningsPerCommonShareTables Earnings per Common Share (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureEarningsPerCommonShare 43 false false R44.htm 31403 - Disclosure - Stock Based Compensation Plan (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlanTables Stock Based Compensation Plan (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlan 44 false false R45.htm 31603 - Disclosure - Regulatory Capital (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureRegulatoryCapitalTables Regulatory Capital (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureRegulatoryCapital 45 false false R46.htm 31703 - Disclosure - Revenue (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureRevenueTables Revenue (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureRevenue 46 false false R47.htm 31803 - Disclosure - Other Operating Expenses (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureOtherOperatingExpensesTables Other Operating Expenses (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureOtherOperatingExpenses 47 false false R48.htm 32003 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureAccumulatedOtherComprehensiveIncomeLossTables Accumulated Other Comprehensive Income (Loss) (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureAccumulatedOtherComprehensiveIncomeLoss 48 false false R49.htm 32103 - Disclosure - Parent Company Financials (Tables) Sheet http://www.johnmarshallbank.com/role/DisclosureParentCompanyFinancialsTables Parent Company Financials (Tables) Tables http://www.johnmarshallbank.com/role/DisclosureParentCompanyFinancials 49 false false R50.htm 40101 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Restriction on Dividends (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyRestrictionOnDividendsDetails Nature of Business and Summary of Significant Accounting Policy - Restriction on Dividends (Details) Details 50 false false R51.htm 40102 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Concentration of Credit Risk (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyConcentrationOfCreditRiskDetails Nature of Business and Summary of Significant Accounting Policy - Concentration of Credit Risk (Details) Details 51 false false R52.htm 40103 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Bank Premises and Equipment (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyBankPremisesAndEquipmentDetails Nature of Business and Summary of Significant Accounting Policy - Bank Premises and Equipment (Details) Details 52 false false R53.htm 40104 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Other Real Estate Owned (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyOtherRealEstateOwnedDetails Nature of Business and Summary of Significant Accounting Policy - Other Real Estate Owned (Details) Details 53 false false R54.htm 40105 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Income Taxes (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyIncomeTaxesDetails Nature of Business and Summary of Significant Accounting Policy - Income Taxes (Details) Details http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyPolicies 54 false false R55.htm 40106 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Advertising Costs (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyAdvertisingCostsDetails Nature of Business and Summary of Significant Accounting Policy - Advertising Costs (Details) Details 55 false false R56.htm 40107 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Recent Accounting Pronouncements - General Information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyRecentAccountingPronouncementsGeneralInformationDetails Nature of Business and Summary of Significant Accounting Policy - Recent Accounting Pronouncements - General Information (Details) Details 56 false false R57.htm 40108 - Disclosure - Nature of Business and Summary of Significant Accounting Policy - Recent Accounting Pronouncements - Adjustments (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureNatureOfBusinessAndSummaryOfSignificantAccountingPolicyRecentAccountingPronouncementsAdjustmentsDetails Nature of Business and Summary of Significant Accounting Policy - Recent Accounting Pronouncements - Adjustments (Details) Details 57 false false R58.htm 40201 - Disclosure - Investment Securities - Amortized Cost and Fair Value - Held-to-maturity Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesAmortizedCostAndFairValueHeldToMaturitySecuritiesDetails Investment Securities - Amortized Cost and Fair Value - Held-to-maturity Securities (Details) Details 58 false false R59.htm 40202 - Disclosure - Investment Securities - Amortized Cost and Fair Value - Available-for-sale Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesAmortizedCostAndFairValueAvailableForSaleSecuritiesDetails Investment Securities - Amortized Cost and Fair Value - Available-for-sale Securities (Details) Details 59 false false R60.htm 40203 - Disclosure - Investment Securities - Transfers (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesTransfersDetails Investment Securities - Transfers (Details) Details 60 false false R61.htm 40204 - Disclosure - Investment Securities - Additional Information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesAdditionalInformationDetails Investment Securities - Additional Information (Details) Details 61 false false R62.htm 40205 - Disclosure - Investment Securities - Pledged Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesPledgedSecuritiesDetails Investment Securities - Pledged Securities (Details) Details 62 false false R63.htm 40206 - Disclosure - Investment Securities - Securities in a Gross Unrealized Loss Position - Held-to-maturity Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesSecuritiesInGrossUnrealizedLossPositionHeldToMaturitySecuritiesDetails Investment Securities - Securities in a Gross Unrealized Loss Position - Held-to-maturity Securities (Details) Details 63 false false R64.htm 40207 - Disclosure - Investment Securities - Securities in a Gross Unrealized Loss Position - Available-for-sale Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesSecuritiesInGrossUnrealizedLossPositionAvailableForSaleSecuritiesDetails Investment Securities - Securities in a Gross Unrealized Loss Position - Available-for-sale Securities (Details) Details 64 false false R65.htm 40208 - Disclosure - Investment Securities - Securities in a Gross Unrealized Loss Position - Positions (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesSecuritiesInGrossUnrealizedLossPositionPositionsDetails Investment Securities - Securities in a Gross Unrealized Loss Position - Positions (Details) Details 65 false false R66.htm 40209 - Disclosure - Investment Securities - Contractual Maturities of Investment Securities - Held-to-maturity Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesContractualMaturitiesOfInvestmentSecuritiesHeldToMaturitySecuritiesDetails Investment Securities - Contractual Maturities of Investment Securities - Held-to-maturity Securities (Details) Details 66 false false R67.htm 40210 - Disclosure - Investment Securities - Contractual Maturities of Investment Securities - Available-for-sale Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesContractualMaturitiesOfInvestmentSecuritiesAvailableForSaleSecuritiesDetails Investment Securities - Contractual Maturities of Investment Securities - Available-for-sale Securities (Details) Details 67 false false R68.htm 40211 - Disclosure - Investment Securities - Restricted Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesRestrictedSecuritiesDetails Investment Securities - Restricted Securities (Details) Details 68 false false R69.htm 40212 - Disclosure - Investment Securities - Equity Securities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureInvestmentSecuritiesEquitySecuritiesDetails Investment Securities - Equity Securities (Details) Details 69 false false R70.htm 40301 - Disclosure - Loans (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLoansDetails Loans (Details) Details http://www.johnmarshallbank.com/role/DisclosureLoansTables 70 false false R71.htm 40401 - Disclosure - Allowance for Loan Losses - Additional information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesAdditionalInformationDetails Allowance for Loan Losses - Additional information (Details) Details 71 false false R72.htm 40402 - Disclosure - Allowance for Loan Losses - Allowance for loan losses activity (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesAllowanceForLoanLossesActivityDetails Allowance for Loan Losses - Allowance for loan losses activity (Details) Details 72 false false R73.htm 40403 - Disclosure - Allowance for Loan Losses - Balance of allowance for loan losses (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesBalanceOfAllowanceForLoanLossesDetails Allowance for Loan Losses - Balance of allowance for loan losses (Details) Details 73 false false R74.htm 40404 - Disclosure - Allowance for Loan Losses - Impaired loans (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesImpairedLoansDetails Allowance for Loan Losses - Impaired loans (Details) Details 74 false false R75.htm 40405 - Disclosure - Allowance for Loan Losses - Past due and non-accrual loans (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesPastDueAndNonAccrualLoansDetails Allowance for Loan Losses - Past due and non-accrual loans (Details) Details 75 false false R76.htm 40406 - Disclosure - Allowance for Loan Losses - Schedule of credit quality information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesScheduleOfCreditQualityInformationDetails Allowance for Loan Losses - Schedule of credit quality information (Details) Details 76 false false R77.htm 40407 - Disclosure - Allowance for Loan Losses - Schedule of loan restructuring modification of loans (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAllowanceForLoanLossesScheduleOfLoanRestructuringModificationOfLoansDetails Allowance for Loan Losses - Schedule of loan restructuring modification of loans (Details) Details 77 false false R78.htm 40501 - Disclosure - Derivatives (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureDerivativesDetails Derivatives (Details) Details http://www.johnmarshallbank.com/role/DisclosureDerivativesTables 78 false false R79.htm 40601 - Disclosure - Bank Premises and Equipment, Net - Tabular Disclosure (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureBankPremisesAndEquipmentNetTabularDisclosureDetails Bank Premises and Equipment, Net - Tabular Disclosure (Details) Details 79 false false R80.htm 40602 - Disclosure - Bank Premises and Equipment, Net - Depreciation Expense (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureBankPremisesAndEquipmentNetDepreciationExpenseDetails Bank Premises and Equipment, Net - Depreciation Expense (Details) Details 80 false false R81.htm 40701 - Disclosure - Deposits and Borrowings - Deposits (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureDepositsAndBorrowingsDepositsDetails Deposits and Borrowings - Deposits (Details) Details 81 false false R82.htm 40702 - Disclosure - Deposits and Borrowings - Long-term Debt (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureDepositsAndBorrowingsLongTermDebtDetails Deposits and Borrowings - Long-term Debt (Details) Details 82 false false R83.htm 40703 - Disclosure - Deposits and Borrowings - Additional Information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureDepositsAndBorrowingsAdditionalInformationDetails Deposits and Borrowings - Additional Information (Details) Details 83 false false R84.htm 40704 - Disclosure - Deposits and Borrowings - Time deposits and FHLB advances by contractual maturity (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureDepositsAndBorrowingsTimeDepositsAndFhlbAdvancesByContractualMaturityDetails Deposits and Borrowings - Time deposits and FHLB advances by contractual maturity (Details) Details 84 false false R85.htm 40801 - Disclosure - Leases - Assets and Liabilities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesAssetsAndLiabilitiesDetails Leases - Assets and Liabilities (Details) Details 85 false false R86.htm 40802 - Disclosure - Leases - Additional Information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesAdditionalInformationDetails Leases - Additional Information (Details) Details 86 false false R87.htm 40803 - Disclosure - Leases - Cost of Leases (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesCostOfLeasesDetails Leases - Cost of Leases (Details) Details 87 false false R88.htm 40804 - Disclosure - Leases - Cash Paid (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesCashPaidDetails Leases - Cash Paid (Details) Details 88 false false R89.htm 40805 - Disclosure - Leases - Lease Maturity Schedule (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesLeaseMaturityScheduleDetails Leases - Lease Maturity Schedule (Details) Details 89 false false R90.htm 40806 - Disclosure - Leases - Gross Difference (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesGrossDifferenceDetails Leases - Gross Difference (Details) Details 90 false false R91.htm 40807 - Disclosure - Leases - Rent Expense (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLeasesRentExpenseDetails Leases - Rent Expense (Details) Details 91 false false R92.htm 40901 - Disclosure - Income Taxes - Deferred Tax Assets and Liabilities (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureIncomeTaxesDeferredTaxAssetsAndLiabilitiesDetails Income Taxes - Deferred Tax Assets and Liabilities (Details) Details 92 false false R93.htm 40902 - Disclosure - Income Taxes - Provision for Income Taxes (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureIncomeTaxesProvisionForIncomeTaxesDetails Income Taxes - Provision for Income Taxes (Details) Details 93 false false R94.htm 40903 - Disclosure - Income Taxes - Effective Income Tax Reconciliation (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureIncomeTaxesEffectiveIncomeTaxReconciliationDetails Income Taxes - Effective Income Tax Reconciliation (Details) Details 94 false false R95.htm 41101 - Disclosure - Commitments and Contingencies (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureCommitmentsAndContingenciesDetails Commitments and Contingencies (Details) Details http://www.johnmarshallbank.com/role/DisclosureCommitmentsAndContingenciesTables 95 false false R96.htm 41201 - Disclosure - Fair Value Measurements - Fair value of assets measured at fair value on a recurring basis (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureFairValueMeasurementsFairValueOfAssetsMeasuredAtFairValueOnRecurringBasisDetails Fair Value Measurements - Fair value of assets measured at fair value on a recurring basis (Details) Details 96 false false R97.htm 41202 - Disclosure - Fair Value Measurements - Carrying value and estimated fair value of financial instruments (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureFairValueMeasurementsCarryingValueAndEstimatedFairValueOfFinancialInstrumentsDetails Fair Value Measurements - Carrying value and estimated fair value of financial instruments (Details) Details 97 false false R98.htm 41203 - Disclosure - Fair Value Measurements - Additional information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureFairValueMeasurementsAdditionalInformationDetails Fair Value Measurements - Additional information (Details) Details 98 false false R99.htm 41301 - Disclosure - Earnings per Common Share - Computation of earnings per share (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureEarningsPerCommonShareComputationOfEarningsPerShareDetails Earnings per Common Share - Computation of earnings per share (Details) Details 99 false false R100.htm 41302 - Disclosure - Earnings per Common Share - Additional information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureEarningsPerCommonShareAdditionalInformationDetails Earnings per Common Share - Additional information (Details) Details 100 false false R101.htm 41401 - Disclosure - Stock Based Compensation Plan (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlanDetails Stock Based Compensation Plan (Details) Details http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlanTables 101 false false R102.htm 41402 - Disclosure - Stock Based Compensation Plan - Summary of Stock Options Activity (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlanSummaryOfStockOptionsActivityDetails Stock Based Compensation Plan - Summary of Stock Options Activity (Details) Details 102 false false R103.htm 41403 - Disclosure - Stock Based Compensation Plan - Summary of Stock Options Outstanding and Exercisable (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlanSummaryOfStockOptionsOutstandingAndExercisableDetails Stock Based Compensation Plan - Summary of Stock Options Outstanding and Exercisable (Details) Details 103 false false R104.htm 41404 - Disclosure - Stock Based Compensation Plan - Summary of Restricted Stock Awards (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureStockBasedCompensationPlanSummaryOfRestrictedStockAwardsDetails Stock Based Compensation Plan - Summary of Restricted Stock Awards (Details) Details 104 false false R105.htm 41501 - Disclosure - Employee Benefit Plans - Defined Contribution Plan (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureEmployeeBenefitPlansDefinedContributionPlanDetails Employee Benefit Plans - Defined Contribution Plan (Details) Details 105 false false R106.htm 41502 - Disclosure - Employee Benefit Plans - Deferred Compensation Arrangement (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureEmployeeBenefitPlansDeferredCompensationArrangementDetails Employee Benefit Plans - Deferred Compensation Arrangement (Details) Details 106 false false R107.htm 41601 - Disclosure - Regulatory Capital (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureRegulatoryCapitalDetails Regulatory Capital (Details) Details http://www.johnmarshallbank.com/role/DisclosureRegulatoryCapitalTables 107 false false R108.htm 41602 - Disclosure - Regulatory Capital - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureRegulatoryCapitalScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsDetails Regulatory Capital - Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations (Details) Details 108 false false R109.htm 41701 - Disclosure - Revenue - Components of Non-interest Income (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureRevenueComponentsOfNonInterestIncomeDetails Revenue - Components of Non-interest Income (Details) Details 109 false false R110.htm 41702 - Disclosure - Revenue - Additional information (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureRevenueAdditionalInformationDetails Revenue - Additional information (Details) Details 110 false false R111.htm 41801 - Disclosure - Other Operating Expenses (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureOtherOperatingExpensesDetails Other Operating Expenses (Details) Details http://www.johnmarshallbank.com/role/DisclosureOtherOperatingExpensesTables 111 false false R112.htm 41901 - Disclosure - Low Income Housing Tax Credit Investments (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureLowIncomeHousingTaxCreditInvestmentsDetails Low Income Housing Tax Credit Investments (Details) Details http://www.johnmarshallbank.com/role/DisclosureLowIncomeHousingTaxCreditInvestments 112 false false R113.htm 42001 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureAccumulatedOtherComprehensiveIncomeLossDetails Accumulated Other Comprehensive Income (Loss) (Details) Details http://www.johnmarshallbank.com/role/DisclosureAccumulatedOtherComprehensiveIncomeLossTables 113 false false R114.htm 42101 - Disclosure - Parent Company Financials - Condensed Balance Sheets (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureParentCompanyFinancialsCondensedBalanceSheetsDetails Parent Company Financials - Condensed Balance Sheets (Details) Details 114 false false R115.htm 42102 - Disclosure - Parent Company Financials - Condensed Statements of Income (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureParentCompanyFinancialsCondensedStatementsOfIncomeDetails Parent Company Financials - Condensed Statements of Income (Details) Details 115 false false R116.htm 42103 - Disclosure - Parent Company Financials - Statements of Cash Flows (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureParentCompanyFinancialsStatementsOfCashFlowsDetails Parent Company Financials - Statements of Cash Flows (Details) Details 116 false false R117.htm 42201 - Disclosure - Related Party Transactions (Details) Sheet http://www.johnmarshallbank.com/role/DisclosureRelatedPartyTransactionsDetails Related Party Transactions (Details) Details http://www.johnmarshallbank.com/role/DisclosureRelatedPartyTransactions 117 false false All Reports Book All Reports [ix-0514-Hidden-Fact-Eligible-For-Transform] WARN: 3 fact(s) appearing in ix:hidden were eligible for transformation: us-gaap:DerivativeFairValueOfDerivativeLiabilityAmountNotOffsetAgainstCollateral, us-gaap:PropertyPlantAndEquipmentUsefulLife, us-gaap:ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1 - jmsb-20221231x10k.htm 9 [ix-0514-Hidden-Fact-Not-Referenced] WARN: 2 fact(s) appearing in ix:hidden were not referenced by any -sec-ix-hidden style property: us-gaap:CommitmentsAndContingencies - jmsb-20221231x10k.htm 9 jmsb-20221231x10k.htm jmsb-20221231.xsd jmsb-20221231_cal.xml jmsb-20221231_def.xml jmsb-20221231_lab.xml jmsb-20221231_pre.xml jmsb-20221231xex21.htm jmsb-20221231xex23d1.htm jmsb-20221231xex31d1.htm jmsb-20221231xex31d2.htm jmsb-20221231xex32d1.htm jmsb-20221231xex4d3.htm jmsb-20221231x10k009.jpg http://fasb.org/srt/2022 http://fasb.org/us-gaap/2022 http://xbrl.sec.gov/dei/2022 true true