3.26.1 html 765 493 1 true 164 0 false 9 false false R1.htm 75000 - Document - Document and Entity Information Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 75010 - Statement - Consolidated Balance Sheets (Unaudited) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnaudited Consolidated Balance Sheets (Unaudited) Statements 2 false false R3.htm 75020 - Statement - Consolidated Balance Sheets (Unaudited) (Parenthetical) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical Consolidated Balance Sheets (Unaudited) (Parenthetical) Statements 3 false false R4.htm 75030 - Statement - Consolidated Statements of Income (Unaudited) Sheet http://www.trustmark.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfIncomeUnaudited Consolidated Statements of Income (Unaudited) Statements 4 false false R5.htm 75040 - Statement - Consolidated Statements of Comprehensive Income (Unaudited) Sheet http://www.trustmark.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfComprehensiveIncomeUnaudited Consolidated Statements of Comprehensive Income (Unaudited) Statements 5 false false R6.htm 75050 - Statement - Consolidated Statements of Changes in Shareholders' Equity (Unaudited) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_StatementConsolidatedStatementsOfChangesInShareholdersEquityUnaudited Consolidated Statements of Changes in Shareholders' Equity (Unaudited) Statements 6 false false R7.htm 75060 - Statement - Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) (Unaudited) Sheet http://www.trustmark.com/20260331/taxonomy/role/StatementConsolidatedStatementsOfChangesInShareholdersEquityParentheticalUnaudited Consolidated Statements of Changes in Shareholders' Equity (Parenthetical) (Unaudited) Statements 7 false false R8.htm 75070 - Statement - Consolidated Statements of Cash Flows (Unaudited) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_StatementConsolidatedStatementsOfCashFlowsUnaudited Consolidated Statements of Cash Flows (Unaudited) Statements 8 false false R9.htm 995410 - Disclosure - Pay vs Performance Disclosure Sheet http://xbrl.sec.gov/ecd/role/PvpDisclosure Pay vs Performance Disclosure Notes 9 false false R10.htm 995445 - Disclosure - Insider Trading Arrangements Sheet http://xbrl.sec.gov/ecd/role/InsiderTradingArrangements Insider Trading Arrangements Notes 10 false false R11.htm 995455 - Disclosure - Business, Basis of Financial Statement Presentation and Principles of Consolidation Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureBusinessBasisOfFinancialStatementPresentationAndPrinciplesOfConsolidation Business, Basis of Financial Statement Presentation and Principles of Consolidation Notes 11 false false R12.htm 995475 - Disclosure - Securities Available for Sale and Held to Maturity Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleAndHeldToMaturity Securities Available for Sale and Held to Maturity Notes 12 false false R13.htm 995485 - Disclosure - LHFI and ACL, LHFI Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfi LHFI and ACL, LHFI Notes 13 false false R14.htm 995495 - Disclosure - Mortgage Banking Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureMortgageBanking Mortgage Banking Notes 14 false false R15.htm 995505 - Disclosure - Other Real Estate Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureOtherRealEstate Other Real Estate Notes 15 false false R16.htm 995515 - Disclosure - Leases Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureLeases Leases Notes 16 false false R17.htm 995525 - Disclosure - Deposits Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDeposits Deposits Notes 17 false false R18.htm 995545 - Disclosure - Revenue from Contracts with Customers Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureRevenueFromContractsWithCustomers Revenue from Contracts with Customers Notes 18 false false R19.htm 995555 - Disclosure - Defined Benefit and Other Postretirement Benefits Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDefinedBenefitAndOtherPostretirementBenefits Defined Benefit and Other Postretirement Benefits Notes 19 false false R20.htm 995565 - Disclosure - Stock and Incentive Compensation Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStockAndIncentiveCompensation Stock and Incentive Compensation Notes 20 false false R21.htm 995575 - Disclosure - Contingencies Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureContingencies Contingencies Notes 21 false false R22.htm 995585 - Disclosure - EPS Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureEps EPS Notes 22 false false R23.htm 995595 - Disclosure - Statements of Cash Flows Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStatementsOfCashFlows Statements of Cash Flows Notes 23 false false R24.htm 995605 - Disclosure - Shareholders' Equity Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureShareholdersEquity Shareholders' Equity Notes 24 false false R25.htm 995615 - Disclosure - Fair Value Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValue Fair Value Notes 25 false false R26.htm 995625 - Disclosure - Derivative Financial Instruments Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDerivativeFinancialInstruments Derivative Financial Instruments Notes 26 false false R27.htm 995635 - Disclosure - Segment Information Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSegmentInformation Segment Information Notes 27 false false R28.htm 995645 - Disclosure - Accounting Policies Recently Adopted and Pending Accounting Pronouncements Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureAccountingPoliciesRecentlyAdoptedAndPendingAccountingPronouncements Accounting Policies Recently Adopted and Pending Accounting Pronouncements Notes 28 false false R29.htm 995655 - Disclosure - Accounting Policies Recently Adopted and Pending Accounting Pronouncements (Policies) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureAccountingPoliciesRecentlyAdoptedAndPendingAccountingPronouncementsPolicies Accounting Policies Recently Adopted and Pending Accounting Pronouncements (Policies) Policies http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureAccountingPoliciesRecentlyAdoptedAndPendingAccountingPronouncements 29 false false R30.htm 995675 - Disclosure - Securities Available for Sale and Held to Maturity (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleAndHeldToMaturityTables Securities Available for Sale and Held to Maturity (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleAndHeldToMaturity 30 false false R31.htm 995685 - Disclosure - LHFI and ACL, LHFI (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiTables LHFI and ACL, LHFI (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfi 31 false false R32.htm 995695 - Disclosure - Mortgage Banking (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureMortgageBankingTables Mortgage Banking (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureMortgageBanking 32 false false R33.htm 995705 - Disclosure - Other Real Estate (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureOtherRealEstateTables Other Real Estate (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureOtherRealEstate 33 false false R34.htm 995715 - Disclosure - Leases (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureLeasesTables Leases (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureLeases 34 false false R35.htm 995725 - Disclosure - Deposits (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDepositsTables Deposits (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDeposits 35 false false R36.htm 995745 - Disclosure - Revenue from Contracts with Customers (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureRevenueFromContractsWithCustomersTables Revenue from Contracts with Customers (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureRevenueFromContractsWithCustomers 36 false false R37.htm 995755 - Disclosure - Defined Benefit and Other Postretirement Benefits (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDefinedBenefitAndOtherPostretirementBenefitsTables Defined Benefit and Other Postretirement Benefits (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDefinedBenefitAndOtherPostretirementBenefits 37 false false R38.htm 995765 - Disclosure - Stock and Incentive Compensation (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStockAndIncentiveCompensationTables Stock and Incentive Compensation (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStockAndIncentiveCompensation 38 false false R39.htm 995775 - Disclosure - Contingencies (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureContingenciesTables Contingencies (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureContingencies 39 false false R40.htm 995785 - Disclosure - EPS (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureEpsTables EPS (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/DisclosureEps 40 false false R41.htm 995795 - Disclosure - Statements of Cash Flows (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStatementsOfCashFlowsTables Statements of Cash Flows (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStatementsOfCashFlows 41 false false R42.htm 995805 - Disclosure - Shareholders' Equity (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureShareholdersEquityTables Shareholders' Equity (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureShareholdersEquity 42 false false R43.htm 995815 - Disclosure - Fair Value (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValueTables Fair Value (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValue 43 false false R44.htm 995825 - Disclosure - Derivative Financial Instruments (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDerivativeFinancialInstrumentsTables Derivative Financial Instruments (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDerivativeFinancialInstruments 44 false false R45.htm 995835 - Disclosure - Segment Information (Tables) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSegmentInformationTables Segment Information (Tables) Tables http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSegmentInformation 45 false false R46.htm 995885 - Disclosure - Securities Available for Sale and Held to Maturity - Amortized Cost and Estimated Fair Value of Available for Sale and Held to Maturity Securities (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleAndHeldToMaturityAmortizedCostAndEstimatedFairValueOfAvailableForSaleAndHeldToMaturitySecuritiesDetails Securities Available for Sale and Held to Maturity - Amortized Cost and Estimated Fair Value of Available for Sale and Held to Maturity Securities (Details) Details 46 false false R47.htm 995895 - Disclosure - Securities Available for Sale and Held to Maturity - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleAndHeldToMaturityAdditionalInformationDetails Securities Available for Sale and Held to Maturity - Additional Information (Details) Details 47 false false R48.htm 995905 - Disclosure - Securities Available for Sale and Held to Maturity - Securities Held to Maturity by Credit Rating, as Determined by Moody's (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureSecuritiesAvailableForSaleAndHeldToMaturitySecuritiesHeldToMaturityByCreditRatingAsDeterminedByMoodysDetails Securities Available for Sale and Held to Maturity - Securities Held to Maturity by Credit Rating, as Determined by Moody's (Details) Details 48 false false R49.htm 995915 - Disclosure - Securities Available for Sale and Held to Maturity - Securities with Gross Unrealized Losses, Segregated by Length of Impairment (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleAndHeldToMaturitySecuritiesWithGrossUnrealizedLossesSegregatedByLengthOfImpairmentDetails Securities Available for Sale and Held to Maturity - Securities with Gross Unrealized Losses, Segregated by Length of Impairment (Details) Details 49 false false R50.htm 995925 - Disclosure - Securities Available for Sale and Held to Maturity - Contractual Maturities of Available for Sale and Held to Maturity Securities (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSecuritiesAvailableForSaleAndHeldToMaturityContractualMaturitiesOfAvailableForSaleAndHeldToMaturitySecuritiesDetails Securities Available for Sale and Held to Maturity - Contractual Maturities of Available for Sale and Held to Maturity Securities (Details) Details 50 false false R51.htm 995965 - Disclosure - LHFI and ACL, LHFI - Loan Portfolio Held for Investment (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiLoanPortfolioHeldForInvestmentDetails LHFI and ACL, LHFI - Loan Portfolio Held for Investment (Details) Details 51 false false R52.htm 995975 - Disclosure - LHFI and ACL, LHFI - Additional Information (Details 1) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiAdditionalInformationDetails1 LHFI and ACL, LHFI - Additional Information (Details 1) Details 52 false false R53.htm 995985 - Disclosure - LHFI and ACL, LHFI - Schedule of Amortized Cost Basis of Loans on Nonaccrual Status (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiScheduleOfAmortizedCostBasisOfLoansOnNonaccrualStatusDetails LHFI and ACL, LHFI - Schedule of Amortized Cost Basis of Loans on Nonaccrual Status (Details) Details 53 false false R54.htm 995995 - Disclosure - LHFI and ACL, LHFI - Aging Analysis of Past Due and Nonaccrual LHFI by Loan Type (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiAgingAnalysisOfPastDueAndNonaccrualLhfiByLoanTypeDetails LHFI and ACL, LHFI - Aging Analysis of Past Due and Nonaccrual LHFI by Loan Type (Details) Details 54 false false R55.htm 996005 - Disclosure - LHFI and ACL, LHFI - Impact of Modifications Classified as Troubled Debt Restructurings (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiImpactOfModificationsClassifiedAsTroubledDebtRestructuringsDetails LHFI and ACL, LHFI - Impact of Modifications Classified as Troubled Debt Restructurings (Details) Details 55 false false R56.htm 996015 - Disclosure - LHFI and ACL, LHFI - Troubled debt restructurings on financial effect (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiTroubledDebtRestructuringsOnFinancialEffectDetails LHFI and ACL, LHFI - Troubled debt restructurings on financial effect (Details) Details 56 false false R57.htm 996025 - Disclosure - LHFI and ACL, LHFI - Troubled Debt Restructuring Subsequently Defaulted (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiTroubledDebtRestructuringSubsequentlyDefaultedDetails LHFI and ACL, LHFI - Troubled Debt Restructuring Subsequently Defaulted (Details) Details 57 false false R58.htm 996035 - Disclosure - LHFI and ACL, LHFI - Past Due Modifications Related to Loans Held For Investment (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiPastDueModificationsRelatedToLoansHeldForInvestmentDetails LHFI and ACL, LHFI - Past Due Modifications Related to Loans Held For Investment (Details) Details 58 false false R59.htm 996045 - Disclosure - LHFI and ACL, LHFI - Schedule of Amortized Cost Basis of Collateral-Dependent Loans by Class of Loans and Collateral Type (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiScheduleOfAmortizedCostBasisOfCollateraldependentLoansByClassOfLoansAndCollateralTypeDetails LHFI and ACL, LHFI - Schedule of Amortized Cost Basis of Collateral-Dependent Loans by Class of Loans and Collateral Type (Details) Details 59 false false R60.htm 996055 - Disclosure - LHFI and ACL, LHFI - Additional Information (Details 2) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiAdditionalInformationDetails2 LHFI and ACL, LHFI - Additional Information (Details 2) Details 60 false false R61.htm 996065 - Disclosure - LHFI and ACL, LHFI - Summary of Amortized Cost Basis of Loans by Credit Quality Indicator (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiSummaryOfAmortizedCostBasisOfLoansByCreditQualityIndicatorDetails LHFI and ACL, LHFI - Summary of Amortized Cost Basis of Loans by Credit Quality Indicator (Details) Details 61 false false R62.htm 996075 - Disclosure - LHFI and ACL, LHFI - Summary of Trustmark's Portfolio Segments, Loan Classes, Loan Pools and the ACL Methodology and Loss Drivers (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiSummaryOfTrustmarksPortfolioSegmentsLoanClassesLoanPoolsAndTheAclMethodologyAndLossDriversDetails LHFI and ACL, LHFI - Summary of Trustmark's Portfolio Segments, Loan Classes, Loan Pools and the ACL Methodology and Loss Drivers (Details) Details 62 false false R63.htm 996085 - Disclosure - LHFI and ACL, LHFI - Summary of Balance in Allowance for Loan Losses (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiSummaryOfBalanceInAllowanceForLoanLossesDetails LHFI and ACL, LHFI - Summary of Balance in Allowance for Loan Losses (Details) Details 63 false false R64.htm 996095 - Disclosure - LHFI and ACL, LHFI - Change in Allowance for Loan Losses (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLhfiAndAclLhfiChangeInAllowanceForLoanLossesDetails LHFI and ACL, LHFI - Change in Allowance for Loan Losses (Details) Details 64 false false R65.htm 996105 - Disclosure - Mortgage Banking - Schedule of Activity in the Mortgage Servicing Rights (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureMortgageBankingScheduleOfActivityInMortgageServicingRightsDetails Mortgage Banking - Schedule of Activity in the Mortgage Servicing Rights (Details) Details 65 false false R66.htm 996115 - Disclosure - Mortgage Banking - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureMortgageBankingAdditionalInformationDetails Mortgage Banking - Additional Information (Details) Details 66 false false R67.htm 996125 - Disclosure - Mortgage Banking - Schedule of Mortgage Loans Sold and Serviced for Others (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureMortgageBankingScheduleOfMortgageLoansSoldAndServicedForOthersDetails Mortgage Banking - Schedule of Mortgage Loans Sold and Serviced for Others (Details) Details 67 false false R68.htm 996135 - Disclosure - Other Real Estate - Changes and Gains (Losses), Net on Other Real Estate (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureOtherRealEstateChangesAndGainsLossesNetOnOtherRealEstateDetails Other Real Estate - Changes and Gains (Losses), Net on Other Real Estate (Details) Details 68 false false R69.htm 996145 - Disclosure - Other Real Estate - Other Real Estate, By Type of Property (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureOtherRealEstateOtherRealEstateByTypeOfPropertyDetails Other Real Estate - Other Real Estate, By Type of Property (Details) Details 69 false false R70.htm 996155 - Disclosure - Other Real Estate - Other Real Estate, By Geographic Location (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureOtherRealEstateOtherRealEstateByGeographicLocationDetails Other Real Estate - Other Real Estate, By Geographic Location (Details) Details 70 false false R71.htm 996165 - Disclosure - Other Real Estate - Additional information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureOtherRealEstateAdditionalInformationDetails Other Real Estate - Additional information (Details) Details 71 false false R72.htm 996175 - Disclosure - Leases - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLeasesAdditionalInformationDetails Leases - Additional Information (Details) Details 72 false false R73.htm 996185 - Disclosure - Leases - Components of the Trustmark's Net Investment in its Sales-Type and Direct Financing Leases (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLeasesComponentsOfTheTrustmarksNetInvestmentInItsSalestypeAndDirectFinancingLeasesDetails Leases - Components of the Trustmark's Net Investment in its Sales-Type and Direct Financing Leases (Details) Details 73 false false R74.htm 996195 - Disclosure - Leases - Minimum Future Lease Payments for Trustmark's Leases Receivable (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureLeasesMinimumFutureLeasePaymentsForTrustmarksLeasesReceivableDetails Leases - Minimum Future Lease Payments for Trustmark's Leases Receivable (Details) Details 74 false false R75.htm 996205 - Disclosure - Leases - Components of Net Lease Cost (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureLeasesComponentsOfNetLeaseCostDetails Leases - Components of Net Lease Cost (Details) Details 75 false false R76.htm 996215 - Disclosure - Leases - Cash Payments Included in Measurement of Lease Liabilities (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureLeasesCashPaymentsIncludedInMeasurementOfLeaseLiabilitiesDetails Leases - Cash Payments Included in Measurement of Lease Liabilities (Details) Details 76 false false R77.htm 996225 - Disclosure - Leases - Balance Sheet Information and Weighted-Average Lease Terms and Discount Rates Related to Leases (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureLeasesBalanceSheetInformationAndWeightedAverageLeaseTermsAndDiscountRatesRelatedToLeasesDetails Leases - Balance Sheet Information and Weighted-Average Lease Terms and Discount Rates Related to Leases (Details) Details 77 false false R78.htm 996235 - Disclosure - Leases - Future Minimum Rental Commitments Under Finance and Operating Leases (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureLeasesFutureMinimumRentalCommitmentsUnderFinanceAndOperatingLeasesDetails Leases - Future Minimum Rental Commitments Under Finance and Operating Leases (Details) Details 78 false false R79.htm 996255 - Disclosure - Deposits - Deposits Summary (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDepositsDepositsSummaryDetails Deposits - Deposits Summary (Details) Details 79 false false R80.htm 996285 - Disclosure - Revenue from Contracts with Customers - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureRevenueFromContractsWithCustomersAdditionalInformationDetails Revenue from Contracts with Customers - Additional Information (Details) Details 80 false false R81.htm 996295 - Disclosure - Revenue from Contracts with Customers - Summary of Noninterest Income (Loss) Disaggregated by Reportable Operating Segment and Revenue Stream (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureRevenueFromContractsWithCustomersSummaryOfNoninterestIncomeLossDisaggregatedByReportableOperatingSegmentAndRevenueStreamDetails Revenue from Contracts with Customers - Summary of Noninterest Income (Loss) Disaggregated by Reportable Operating Segment and Revenue Stream (Details) Details 81 false false R82.htm 996305 - Disclosure - Defined Benefit and Other Postretirement Benefits - Net Periodic Benefit Cost (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDefinedBenefitAndOtherPostretirementBenefitsNetPeriodicBenefitCostDetails Defined Benefit and Other Postretirement Benefits - Net Periodic Benefit Cost (Details) Details 82 false false R83.htm 996315 - Disclosure - Defined Benefit and Other Postretirement Benefits - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDefinedBenefitAndOtherPostretirementBenefitsAdditionalInformationDetails Defined Benefit and Other Postretirement Benefits - Additional Information (Details) Details 83 false false R84.htm 996325 - Disclosure - Stock and Incentive Compensation - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStockAndIncentiveCompensationAdditionalInformationDetails Stock and Incentive Compensation - Additional Information (Details) Details 84 false false R85.htm 996335 - Disclosure - Stock and Incentive Compensation - Summary of Stock Plan Activity (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStockAndIncentiveCompensationSummaryOfStockPlanActivityDetails Stock and Incentive Compensation - Summary of Stock Plan Activity (Details) Details 85 false false R86.htm 996345 - Disclosure - Stock and Incentive Compensation - Compensation Expense for Awards and Units Under Stock Plan (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStockAndIncentiveCompensationCompensationExpenseForAwardsAndUnitsUnderStockPlanDetails Stock and Incentive Compensation - Compensation Expense for Awards and Units Under Stock Plan (Details) Details 86 false false R87.htm 996355 - Disclosure - Contingencies - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureContingenciesAdditionalInformationDetails Contingencies - Additional Information (Details) Details 87 false false R88.htm 996365 - Disclosure - Contingencies - Summary of Changes in ACL on Off-Balance Sheet Credit Exposures (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureContingenciesSummaryOfChangesInAclOnOffbalanceSheetCreditExposuresDetails Contingencies - Summary of Changes in ACL on Off-Balance Sheet Credit Exposures (Details) Details 88 false false R89.htm 996375 - Disclosure - EPS - Weighted-Average Shares Used to Calculate Basic and Diluted EPS (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureEpsWeightedaverageSharesUsedToCalculateBasicAndDilutedEpsDetails EPS - Weighted-Average Shares Used to Calculate Basic and Diluted EPS (Details) Details 89 false false R90.htm 996385 - Disclosure - EPS - Weighted-Average Antidilutive Stock Awards for Periods (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureEpsWeightedaverageAntidilutiveStockAwardsForPeriodsDetails EPS - Weighted-Average Antidilutive Stock Awards for Periods (Details) Details 90 false false R91.htm 996395 - Disclosure - Statements of Cash Flows - Cash Flows Supplementary Disclosures (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureStatementsOfCashFlowsCashFlowsSupplementaryDisclosuresDetails Statements of Cash Flows - Cash Flows Supplementary Disclosures (Details) Details 91 false false R92.htm 996405 - Disclosure - Shareholders' Equity - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureShareholdersEquityAdditionalInformationDetails Shareholders' Equity - Additional Information (Details) Details 92 false false R93.htm 996415 - Disclosure - Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureShareholdersEquityTableOfActualRegulatoryCapitalAmountsAndRatiosDetails Shareholders' Equity - Table of Actual Regulatory Capital Amounts and Ratios (Details) Details 93 false false R94.htm 996425 - Disclosure - Shareholders' Equity - Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureShareholdersEquityNetChangeInComponentsOfAccumulatedOtherComprehensiveIncomeLossAndRelatedTaxEffectsDetails Shareholders' Equity - Net Change in Components of Accumulated Other Comprehensive Income (Loss) and the Related Tax Effects (Details) Details 94 false false R95.htm 996435 - Disclosure - Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Income (Loss) (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureShareholdersEquityChangesInBalancesOfComponentOfAccumulatedOtherComprehensiveIncomeLossDetails Shareholders' Equity - Changes in Balances of Component of Accumulated Other Comprehensive Income (Loss) (Details) Details 95 false false R96.htm 996445 - Disclosure - Fair Value - Financial Assets and Liabilities Measured at Fair Value Recurring Basis (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValueFinancialAssetsAndLiabilitiesMeasuredAtFairValueRecurringBasisDetails Fair Value - Financial Assets and Liabilities Measured at Fair Value Recurring Basis (Details) Details 96 false false R97.htm 996455 - Disclosure - Fair Value - Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValueChangesInLevel3AssetsMeasuredAtFairValueOnRecurringBasisDetails Fair Value - Changes in Level 3 Assets Measured at Fair Value on a Recurring Basis (Details) Details 97 false false R98.htm 996465 - Disclosure - Fair Value - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValueAdditionalInformationDetails Fair Value - Additional Information (Details) Details 98 false false R99.htm 996475 - Disclosure - Fair Value - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValueCarryingAmountsAndEstimatedFairValuesOfFinancialInstrumentsDetails Fair Value - Carrying Amounts and Estimated Fair Values of Financial Instruments (Details) Details 99 false false R100.htm 996485 - Disclosure - Fair Value - Fair Value and the Contractual Principal Outstanding of the LHFS (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureFairValueFairValueAndContractualPrincipalOutstandingOfLHFSDetails Fair Value - Fair Value and the Contractual Principal Outstanding of the LHFS (Details) Details 100 false false R101.htm 996495 - Disclosure - Derivative Financial Instruments - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDerivativeFinancialInstrumentsAdditionalInformationDetails Derivative Financial Instruments - Additional Information (Details) Details 101 false false R102.htm 996505 - Disclosure - Derivative Financial Instruments - Fair Value of Derivative Instruments (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDerivativeFinancialInstrumentsFairValueOfDerivativeInstrumentsDetails Derivative Financial Instruments - Fair Value of Derivative Instruments (Details) Details 102 false false R103.htm 996515 - Disclosure - Derivative Financial Instruments - Effects of Derivative Instruments on Statements of Operations (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDerivativeFinancialInstrumentsEffectsOfDerivativeInstrumentsOnStatementsOfOperationsDetails Derivative Financial Instruments - Effects of Derivative Instruments on Statements of Operations (Details) Details 103 false false R104.htm 996525 - Disclosure - Derivative Financial Instruments - Schedule of Amount Included in Other Comprehensive Income (Loss) for Derivative Instruments Designated as Hedges of Cash Flows (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/DisclosureDerivativeFinancialInstrumentsScheduleOfAmountIncludedInOtherComprehensiveIncomeLossForDerivativeInstrumentsDesignatedAsHedgesOf Derivative Financial Instruments - Schedule of Amount Included in Other Comprehensive Income (Loss) for Derivative Instruments Designated as Hedges of Cash Flows (Details) Details 104 false false R105.htm 996535 - Disclosure - Derivative Financial Instruments - Information about Financial Instruments that are Eligible for Offset in the Consolidated Balance Sheets (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureDerivativeFinancialInstrumentsInformationAboutFinancialInstrumentsThatAreEligibleForOffsetInConsolidatedBalanceSheetsDetails Derivative Financial Instruments - Information about Financial Instruments that are Eligible for Offset in the Consolidated Balance Sheets (Details) Details 105 false false R106.htm 996555 - Disclosure - Segment Information - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSegmentInformationAdditionalInformationDetails Segment Information - Additional Information (Details) Details 106 false false R107.htm 996565 - Disclosure - Segment Information - Schedule of Segment Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureSegmentInformationScheduleOfSegmentInformationDetails Segment Information - Schedule of Segment Information (Details) Details 107 false false R108.htm 996585 - Disclosure - Accounting Policies Recently Adopted and Pending Accounting Pronouncements - Additional Information (Details) Sheet http://www.trustmark.com/20260331/taxonomy/role/Role_DisclosureAccountingPoliciesRecentlyAdoptedAndPendingAccountingPronouncementsAdditionalInformationDetails Accounting Policies Recently Adopted and Pending Accounting Pronouncements - Additional Information (Details) Details 108 false false All Reports Book All Reports trmk-20260331.htm trmk-20260331.xsd img223788455_0.jpg http://fasb.org/us-gaap/2025 http://xbrl.sec.gov/dei/2025 http://xbrl.sec.gov/ecd/2025 false false