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Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (1) (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 Region | Dec. 31, 2013 | Dec. 31, 2012
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | $ 96,365,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance | $ 86,982,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance |
Total LHFI With No Related Allowance Recorded | 23,135,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded | 25,643,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded |
Total LHFI With an Allowance Recorded | 56,208,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded | 39,595,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded |
Total Carrying Amount | 79,343,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment | 65,238,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment |
Related Allowance | 12,764,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance | 5,181,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance |
Average Recorded Investment | 72,291,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment | 73,800,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment |
Maximum Concentration Of Loan as a Percentage of Total LHFI (in hundredths) | 10.00%trmk_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposurePercentage |  |
Key market regions | 5 trmk_KeyMarketRegionsInQualitativeReserveAllocation |  |
Loans and Leases Receivable, Related Parties | 95,200,000 us-gaap_LoansAndLeasesReceivableRelatedParties | 89,000,000 us-gaap_LoansAndLeasesReceivableRelatedParties |
New loan advances to related party | 643,100,000 us-gaap_LoansAndLeasesReceivableRelatedPartiesAdditions |  |
Loan repayment by related party | 636,500,000 us-gaap_LoansAndLeasesReceivableRelatedPartiesCollections |  |
Loan decreases from changes in executive officers and directors | 372,000 us-gaap_LoansAndLeasesReceivableRelatedPartiesPeriodIncreaseDecrease |  |
Carrying amounts of nonaccrual LHFI considered for impairment analysis | 79,300,000 trmk_NonaccrualLoansHeldForInvestmentConsideredForImpairmentAnalysisCarryingValue | 65,200,000 trmk_NonaccrualLoansHeldForInvestmentConsideredForImpairmentAnalysisCarryingValue |
Minimum loan amount for loan to be individually assessed for impairment | 500,000 trmk_MinimumLoanAmountForLoanToBeIndividuallyAssessedForImpairment |  |
Nonaccrual Financing Receivable, Specifically Evaluated For Impairment | 47,100,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairment | 31,600,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairment |
Nonaccrual Financing Receivable, Allowance for Credit Losses, Specifically Evaluated For Impairment | 11,300,000 trmk_NonaccrualFinancingReceivableAllowanceForCreditLossesSpecificallyEvaluatedForImpairment | 2,200,000 trmk_NonaccrualFinancingReceivableAllowanceForCreditLossesSpecificallyEvaluatedForImpairment |
Nonaccrual Financing Receivable, Allowance For Credit Losses, Charge-offs, Specifically Evaluated For Impairment | 137,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairmentAllowanceForCreditLossesWriteOffs | 2,500,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairmentAllowanceForCreditLossesWriteOffs | 13,100,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairmentAllowanceForCreditLossesWriteOffs
Nonaccrual Financing Receivable Specifically Evaluated For Impairment Allowance For Credit Losses Provisions | 3,500,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairmentAllowanceForCreditLossesProvisions | 2,900,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairmentAllowanceForCreditLossesProvisions | 1,100,000 trmk_NonaccrualFinancingReceivableSpecificallyEvaluatedForImpairmentAllowanceForCreditLossesProvisions
Nonaccrual Financing Receivable, Not Specifically Evaluated for Impairment | 32,200,000 trmk_NonaccrualFinancingReceivableNotSpecificallyEvaluatedForImpairment | 33,700,000 trmk_NonaccrualFinancingReceivableNotSpecificallyEvaluatedForImpairment |
Nonaccrual Financing Receivable, Allowance for Credit Losses, Not Specifically Evaluated for Impairment | 1,500,000 trmk_NonaccrualFinancingReceivableAllowanceForCreditLossesNotSpecificallyEvaluatedForImpairment | 3,000,000 trmk_NonaccrualFinancingReceivableAllowanceForCreditLossesNotSpecificallyEvaluatedForImpairment |
Classified as Troubled Debt Restructuring LHFI | 11,300,000 trmk_ClassifiedAsTroubledDebtRestructuringLhfi | 14,800,000 trmk_ClassifiedAsTroubledDebtRestructuringLhfi | 24,300,000 trmk_ClassifiedAsTroubledDebtRestructuringLhfi
TDRs comprised of credits with interest only payments | 7,400,000 trmk_TroubledDebtRestructuringsComprisedOfCreditsWithInterestOnlyPayments | 11,100,000 trmk_TroubledDebtRestructuringsComprisedOfCreditsWithInterestOnlyPayments | 21,600,000 trmk_TroubledDebtRestructuringsComprisedOfCreditsWithInterestOnlyPayments
Financing Receivable, Related Allowance | 1,700,000 trmk_FinancingReceivablePostModificationRecordedInvestmentRelatedAllowance | 1,600,000 trmk_FinancingReceivablePostModificationRecordedInvestmentRelatedAllowance | 4,300,000 trmk_FinancingReceivablePostModificationRecordedInvestmentRelatedAllowance
Financing Receivable, Related Charge-offs | 75,000 trmk_FinancingReceivablePostModificationRecordedInvestmentRelatedWriteOffs | 816,000 trmk_FinancingReceivablePostModificationRecordedInvestmentRelatedWriteOffs | 6,000,000 trmk_FinancingReceivablePostModificationRecordedInvestmentRelatedWriteOffs
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member] |  |  |
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | 20,849,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 24,350,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With No Related Allowance Recorded | 7,411,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 9,817,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With an Allowance Recorded | 6,456,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 3,510,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total Carrying Amount | 13,867,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 13,327,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Related Allowance | 2,767,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 989,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Average Recorded Investment | 13,597,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 20,216,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] |  |  |
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | 31,151,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 26,541,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With No Related Allowance Recorded | 1,650,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 3,095,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With an Allowance Recorded | 23,971,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 18,508,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total Carrying Amount | 25,621,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 21,603,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Related Allowance | 450,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 191,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Average Recorded Investment | 23,612,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 24,359,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Loans Secured by Real Estate [Member] | Nonfarm, Nonresidential Properties [Member] |  |  |
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | 27,969,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 24,879,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With No Related Allowance Recorded | 12,868,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 10,225,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With an Allowance Recorded | 12,849,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 11,584,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total Carrying Amount | 25,717,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 21,809,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Related Allowance | 2,787,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 2,307,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Average Recorded Investment | 23,763,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 20,049,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Loans Secured by Real Estate [Member] | Other Real Estate Secured Financing Receivable [Member] |  |  |
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | 1,594,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 1,375,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With No Related Allowance Recorded | 0 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 0 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI With an Allowance Recorded | 1,318,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 1,327,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total Carrying Amount | 1,318,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 1,327,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Related Allowance | 52,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 122,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Average Recorded Investment | 1,322,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | 2,641,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Commercial and Industrial Loans [Member] |  |  |
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | 13,916,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember | 8,702,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember |
Total LHFI With No Related Allowance Recorded | 1,206,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember | 2,506,000 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember |
Total LHFI With an Allowance Recorded | 10,898,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember | 3,780,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember |
Total Carrying Amount | 12,104,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember | 6,286,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember |
Related Allowance | 6,449,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember | 1,253,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember |
Average Recorded Investment | 9,195,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember | 5,513,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansFinancingReceivableMember |
Consumer Loans [Member] |  |  |
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | 152,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | 286,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Total LHFI With No Related Allowance Recorded | 0 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | 0 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Total LHFI With an Allowance Recorded | 88,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | 151,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Total Carrying Amount | 88,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | 151,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Related Allowance | 0 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | 2,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Average Recorded Investment | 120,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | 255,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Other Loans [Member] |  |  |
Loan and Lease Receivables, Impaired [Abstract] |  |  |
Unpaid Principal Balance | 734,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | 849,000 us-gaap_ImpairedFinancingReceivableUnpaidPrincipalBalance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Total LHFI With No Related Allowance Recorded | 0 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | 0 trmk_ImpairedFinancingReceivableNoRelatedAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Total LHFI With an Allowance Recorded | 628,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | 735,000 trmk_ImpairedFinancingReceivableWithAllowanceRecorded / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Total Carrying Amount | 628,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | 735,000 us-gaap_ImpairedFinancingReceivableRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Related Allowance | 259,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | 317,000 us-gaap_ImpairedFinancingReceivableRelatedAllowance / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Average Recorded Investment | $ 682,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | $ 767,000 us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |

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- Definition LHFI classified as TDR. + References No definition available. + Details
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Balance Type: | credit
Period Type: | instant

X
- Definition The maximum concentration for any loan concentration as a percentage of total loans held for investment. + References No definition available. + Details
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- Definition Amount of allowance for credit losses related to financing receivable that has undergone troubled debt restructuring. + References No definition available. + Details
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Balance Type: | credit
Period Type: | instant

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- Definition Reduction to the allowance for credit losses related to financing receivables, excluding covered loans, that have undergone troubled debt restructuring and deemed uncollectible. + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of impaired financing receivable that does not have a related allowance recorded. + References No definition available. + Details
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- Definition Amount of impaired financing receivable that does have an allowance recorded. + References No definition available. + Details
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- Definition Number of key market regions the entity operates that are included in the qualitative reserve allocation review process. + References No definition available. + Details
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X
- Definition The minimum loan amount for a nonaccrual LHFI to be assessed individually for impairment. + References No definition available. + Details
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- Definition The valuation allowance for nonaccrual financing receivables that are expected to be uncollectible that were not specifically evaluated for impairment. + References No definition available. + Details
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- Definition The valuation allowance for nonaccrual financing receivables that are expected to be uncollectible that were specifically evaluated for impairment. + References No definition available. + Details
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- Definition The balance of nonaccrual financing receivables that were not specifically evaluated for impairment. + References No definition available. + Details
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- Definition The balance of nonaccrual financing receivables that were specifically evaluated for impairment. + References No definition available. + Details
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- Definition Charge to expense for nonaccrual financing receivables that are specifically evaluated for impairment and expected to be uncollectible. + References No definition available. + Details
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- Definition Reduction to the allowance for credit losses related to nonaccrual financing receivables specifically evaluated for impairment. + References No definition available. + Details
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- Definition The carrying value of the nonaccrual loans held for investment that were considered for impairment analysis. + References No definition available. + Details
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- Definition Loans Held for Investment classified as Troubled debt restructurings (TDRs) which is primarily comprised of credits with interest only payments. + References No definition available. + Details
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- Definition Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5258-111524 + Details
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- Definition Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 14A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953550-111524 + Details
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- Definition Amount of allowance for credit losses related to recorded investment. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(3) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524 + Details
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- Definition Amount of unpaid principal balance of impaired financing receivables with related allowance for credit losses and without related allowance for credit losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5212-111524 + Details
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- Definition For an unclassified balance sheet, reflects the carrying amount of unpaid loan amounts due from related parties at the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(e)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph e -Article 9 + Details
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- Definition Reflects the amount of new advances made to related parties in the form of loan and lease receivables. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(e)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph e -Article 9 + Details
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- Definition Reflects the amount of collections received from related parties to reduce the carrying amounts of loans and leases receivable due from them. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(e)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph e -Article 9 + Details
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- Definition Reflects the sum for the period of the additions and reductions to related party loans, which when added to the opening balance of related party loan will agree to the ending balance of such loans. This subtotal typically is not reflected. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(e)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Subparagraph e -Article 9 + Details
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