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Shareholders' Equity (Details) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Securities available for sale and transferred securities, Before tax amount [Abstract]      
Unrealized holding (losses) gains arising during the period, Before tax amount $ 17,705,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax $ (67,135,000)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax $ 97,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTax
Reclassification adjustment for net gains realized in net income, Before tax amount (300,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax (485,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax (1,059,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesBeforeTax
Change in net unrealized holding loss on securities transferred to held to maturity, Before tax amount 6,010,000us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax (46,383,000)us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesBeforeTax  
Total securities available for sale and transferred securities, Before tax amount 23,415,000us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax (114,003,000)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax (962,000)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax
Securities available for sale and transferred securities, Tax (expense) benefit [Abstract]      
Unrealized holding losses (gains) arising during the period, Tax (expense) benefit (6,772,000)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax 25,679,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax (37,000)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodTax
Reclassification adjustment for net gains realized in net income, Tax (expense) benefit 115,000us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax 186,000us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax 405,000us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesTax
Change in net unrealized holding loss on securities transferred to held to maturity, Tax (expense) benefit (2,299,000)us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesTax 17,741,000us-gaap_OtherComprehensiveIncomeReclassificationAdjustmentForHeldToMaturityTransferredToAvailableForSaleSecuritiesTax  
Total securities available for sale and transferred securities, Tax (expense) benefit (8,956,000)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax 43,606,000us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax 368,000us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax
Securities available for sale and transferred securities, Net of tax amount: [Abstract]      
Unrealized holding (losses) gains arising during the period, after tax income (expense) 10,933,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax (41,456,000)us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax 60,000us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax
Reclassification adjustment for net gains realized in net income, after tax income (expense) (185,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax (299,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax (654,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax
Change in net unrealized holding loss on securities transferred to held to maturity, after tax income (expense) 3,711,000us-gaap_OtherComprehensiveIncomeLossTransfersFromHeldToMaturityToAvailableForSaleSecuritiesNetOfTax (28,642,000)us-gaap_OtherComprehensiveIncomeLossTransfersFromHeldToMaturityToAvailableForSaleSecuritiesNetOfTax 0us-gaap_OtherComprehensiveIncomeLossTransfersFromHeldToMaturityToAvailableForSaleSecuritiesNetOfTax
Total securities available for sale and transferred securities, after tax income (expense) 14,459,000us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax (70,397,000)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax (594,000)us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
Pension and other postretirement benefit plans, Before tax amount: [Abstract]      
Net change in prior service costs, before tax amount 249,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax 251,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax 52,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostCreditArisingDuringPeriodBeforeTax
Recognized net loss due to BancTrust terminations, before tax amount 1,355,000trmk_OtherComprehensiveIncomeLossAttributableToBancTrustSettlementBeforeTax    
Recognized net loss due to lump sum settlements, before tax amount 905,000us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax 2,225,000us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationBeforeTax  
Recognized net actuarial (loss) gain, before tax amount (21,657,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax 32,742,000us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax 1,354,000us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansNetUnamortizedGainLossArisingDuringPeriodBeforeTax
Total pension and other postretirement benefit plans, before tax amount (19,148,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax 35,218,000us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax 1,406,000us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeTax
Pension and other postretirement benefit plans, Tax (expense) benefit: [Abstract]      
Net change in prior service costs, tax (expense) benefit (95,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBenefitPlanImprovementTaxEffect (96,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBenefitPlanImprovementTaxEffect (20,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansBenefitPlanImprovementTaxEffect
Recognized net loss due to BancTrust Terminations, tax (expense) benefit (518,000)trmk_OtherComprehensiveIncomeSettlementsOfPensionAndNonPensionPostretirementPlanValuationTaxRelatedToBancTrustTerminations    
Recognized net loss due to lump sum settlement, tax (expense) benefit (346,000)us-gaap_OtherComprehensiveIncomeFinalizationOfPensionAndNonPensionPostretirementPlanValuationTax (851,000)us-gaap_OtherComprehensiveIncomeFinalizationOfPensionAndNonPensionPostretirementPlanValuationTax  
Recognized net actuarial (loss) gain, tax (expense) benefit 8,283,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax (12,524,000)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax (518,000)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodTax
Total pension and other postretirement benefit plans, tax (expense) benefit 7,324,000us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax (13,471,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax (538,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax
Pension and other postretirement benefit plans, Net of tax amount [Abstract]      
Net change in prior service costs, after tax income (expense) 154,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax 155,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax 32,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlanNetPriorServiceCostsCreditArisingDuringPeriodNetOfTax
Recognized net loss due to BancTrust terminations after tax income (expense) 837,000trmk_OtherComprehensiveIncomeLossFinalizationOfPensionAndOtherPostretirementBenefitPlanValuationNetOfTaxAttributableToBancTrustTerminations    
Recognized net loss due to settlement after tax income (expense) 559,000us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax 1,374,000us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax 0us-gaap_OtherComprehensiveIncomeLossFinalizationOfPensionAndNonPensionPostretirementPlanValuationNetOfTax
Recognized net actuarial (loss) gain, after tax income (expense) (13,374,000)us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax 20,218,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax 836,000us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax
Total pension and other postretirement benefit plans, after tax income (expense) (11,824,000)us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax 21,747,000us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax 868,000us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax
Derivatives, Before tax amount: [Abstract]      
Change in accumulated gain on effective cash flow hedge derivatives, before tax amount (2,246,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax 2,468,000us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax  
Reclassification adjustment for loss realized in net income, before tax amount (2,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesBeforeTax    
Total cash flow hedge derivatives, before tax benefit (2,248,000)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesBeforeTax    
Derivatives, Tax (expense) benefit: [Abstract]      
Change in accumulated gain on effective cash flow hedge derivatives, tax (expense) benefit 859,000us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax (944,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodTax  
Reclassification adjustment for loss realized in net income, tax (expense) benefit 1,000us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesTax    
Total cash flow hedge derivatives, tax (expense) benefit 860,000us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax    
Derivatives, Net of tax amount: [Abstract]      
Change in the accumulated gain on effective cash flow hedge derivatives, after tax amount (1,387,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax 1,524,000us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax 0us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
Reclassification adjustment for loss realized in net income, after tax amount (1,000)us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax 0us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax
Total cash flow hedge derivatives, after tax amount (1,388,000)us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax 1,524,000us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax  
Total other comprehensive income (loss), Before tax amount 2,019,000us-gaap_OtherComprehensiveIncomeLossBeforeTax (76,317,000)us-gaap_OtherComprehensiveIncomeLossBeforeTax 444,000us-gaap_OtherComprehensiveIncomeLossBeforeTax
Total other comprehensive income (loss), Tax expense (benefit) (772,000)us-gaap_OtherComprehensiveIncomeLossTax 29,191,000us-gaap_OtherComprehensiveIncomeLossTax (170,000)us-gaap_OtherComprehensiveIncomeLossTax
Total other comprehensive income (loss), Net of tax 1,247,000us-gaap_OtherComprehensiveIncomeOtherNetOfTax (47,126,000)us-gaap_OtherComprehensiveIncomeOtherNetOfTax 274,000us-gaap_OtherComprehensiveIncomeOtherNetOfTax
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Opening balance (43,731,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax 3,395,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax 3,121,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Other comprehensive income (loss) before reclassification 1,433,000us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax (46,827,000)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax 928,000us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
Amounts reclassified from accumulated other comprehensive income (loss) (186,000)us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax (299,000)us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax (654,000)us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
Net other comprehensive (loss) income 1,247,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent (47,126,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent 274,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
Ending balance (42,484,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax (43,731,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax 3,395,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
Securities Available for Sale and Transferred Securities [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Opening balance (25,462,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 44,935,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 45,529,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Other comprehensive income (loss) before reclassification 14,644,000us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 (70,098,000)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 60,000us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Amounts reclassified from accumulated other comprehensive income (loss) (185,000)us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 (299,000)us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 (654,000)us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Net other comprehensive (loss) income 14,459,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 (70,397,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 (594,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Ending balance (11,003,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 (25,462,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember		 44,935,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Defined Benefit Pension Items [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Opening balance (19,793,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 (41,540,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 (42,408,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Other comprehensive income (loss) before reclassification (11,824,000)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 21,747,000us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 868,000us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Amounts reclassified from accumulated other comprehensive income (loss) 0us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 0us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 0us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Net other comprehensive (loss) income (11,824,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 21,747,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 868,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Ending balance (31,617,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 (19,793,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember		 (41,540,000)us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Cash Flow Hedge Derivatives [Member]      
Accumulated Other Comprehensive Income (Loss) [Line Items]      
Opening balance 1,524,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 0us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 0us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Other comprehensive income (loss) before reclassification (1,387,000)us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 1,524,000us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 0us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Amounts reclassified from accumulated other comprehensive income (loss) (1,000)us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 0us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 0us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Net other comprehensive (loss) income (1,388,000)us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 1,524,000us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 0us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Ending balance 136,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 1,524,000us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember		 0us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember
Common Shares [Member]      
Dividends on common stock [Abstract]      
Dividend potential for next fiscal year 114,300,000trmk_ProceedingTwoNetIncomeBasisForRegulatorRequiredDividendPaymentBasis
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassAMember		    
Period for which retained net income considered for approval 2 years    
Trustmark Corporation [Member] | Total Capital (to Risk Weighted Assets) [Member]      
Total Capital (to Risk Weighted Assets) [Abstract]      
Actual Regulatory Capital Amount 1,221,292,000us-gaap_Capital
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 1,122,904,000us-gaap_Capital
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Actual Regulatory Capital Ratio (in hundredths) 14.56%us-gaap_CapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 14.18%us-gaap_CapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Amount 671,024,000us-gaap_CapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 633,310,000us-gaap_CapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Ratio (in hundredths) 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Amount    [1]    [1]  
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)    [1]    [1]  
Trustmark Corporation [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]      
Tier 1 Capital (to Risk Weighted Assets) [Abstract]      
Actual Regulatory Capital Amount 1,129,630,000us-gaap_TierOneRiskBasedCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 1,026,858,000us-gaap_TierOneRiskBasedCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Actual Regulatory Capital Ratio (in hundredths) 13.47%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 12.97%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Amount 335,512,000us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 316,655,000us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Ratio (in hundredths) 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Amount    [1]    [1]  
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)    [1]    [1]  
Trustmark Corporation [Member] | Tier 1 Capital (to Average Assets) [Member]      
Tier 1 Capital (to Average Assets) [Abstract]      
Actual Regulatory Capital Amount 1,129,630,000us-gaap_TierOneLeverageCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 1,026,858,000us-gaap_TierOneLeverageCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Actual Regulatory Capital Ratio (in hundredths) 9.63%us-gaap_TierOneLeverageCapitalToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 9.06%us-gaap_TierOneLeverageCapitalToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Minimum Regulatory Capital Required Amount 469,411,000us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 453,487,000us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Minimum Regulatory Capital Required Ratio (in hundredths) 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkCorporationMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Amount    [1]    [1]  
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths)    [1]    [1]  
Trustmark National Bank [Member] | Total Capital (to Risk Weighted Assets) [Member]      
Total Capital (to Risk Weighted Assets) [Abstract]      
Actual Regulatory Capital Amount 1,198,697,000us-gaap_Capital
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 1,076,391,000us-gaap_Capital
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Actual Regulatory Capital Ratio (in hundredths) 14.32%us-gaap_CapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 13.74%us-gaap_CapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Amount 669,856,000us-gaap_CapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 626,672,000us-gaap_CapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Ratio (in hundredths) 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 8.00%us-gaap_CapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Amount 837,320,000us-gaap_CapitalRequiredToBeWellCapitalized
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 783,340,000us-gaap_CapitalRequiredToBeWellCapitalized
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths) 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		 10.00%us-gaap_CapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_TotalCapitalToRiskWeightedAssetsMember		  
Trustmark National Bank [Member] | Tier 1 Capital (to Risk Weighted Assets) [Member]      
Tier 1 Capital (to Risk Weighted Assets) [Abstract]      
Actual Regulatory Capital Amount 1,108,399,000us-gaap_TierOneRiskBasedCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 982,925,000us-gaap_TierOneRiskBasedCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Actual Regulatory Capital Ratio (in hundredths) 13.24%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 12.55%us-gaap_TierOneRiskBasedCapitalToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Amount 334,928,000us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 313,336,000us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Capital Required Ratio (in hundredths) 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 4.00%us-gaap_TierOneRiskBasedCapitalRequiredForCapitalAdequacyToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Amount 502,392,000us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 470,004,000us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalized
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths) 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		 6.00%us-gaap_TierOneRiskBasedCapitalRequiredToBeWellCapitalizedToRiskWeightedAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToRiskWeightedAssetsMember		  
Trustmark National Bank [Member] | Tier 1 Capital (to Average Assets) [Member]      
Tier 1 Capital (to Average Assets) [Abstract]      
Actual Regulatory Capital Amount 1,108,399,000us-gaap_TierOneLeverageCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 982,925,000us-gaap_TierOneLeverageCapital
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Actual Regulatory Capital Ratio (in hundredths) 9.46%us-gaap_TierOneLeverageCapitalToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 8.76%us-gaap_TierOneLeverageCapitalToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Minimum Regulatory Capital Required Amount 468,783,000us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 448,665,000us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacy
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Minimum Regulatory Capital Required Ratio (in hundredths) 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 4.00%us-gaap_TierOneLeverageCapitalRequiredForCapitalAdequacyToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Amount $ 585,979,000us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 $ 560,831,000us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
Minimum Regulatory Provision to be Well-Capitalized Ratio (in hundredths) 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		 5.00%us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalizedToAverageAssets
/ dei_LegalEntityAxis
= trmk_TrustmarkNationalBankMember
/ trmk_TypeOfCapitalComparisonAxis
= trmk_Tier1CapitalToAverageAssetsMember		  
[1] n/a