XML 67 R59.htm IDEA: XBRL DOCUMENT v2.4.1.9
Securities Available for Sale and Held to Maturity (1) (Details) (USD $)
3 Months Ended 12 Months Ended 3 Months Ended
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Mar. 31, 2014
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months $ 2,108,340,000trmk_EstimatedFairValueLessThan12Months $ 590,965,000trmk_EstimatedFairValueLessThan12Months $ 2,108,340,000trmk_EstimatedFairValueLessThan12Months    
Estimated fair value, 12 months or more 24,415,000trmk_EstimatedFairValue12MonthsOrMore 522,230,000trmk_EstimatedFairValue12MonthsOrMore 24,415,000trmk_EstimatedFairValue12MonthsOrMore    
Total estimated fair value 2,132,755,000trmk_TotalEstimatedFairValue 1,113,195,000trmk_TotalEstimatedFairValue 2,132,755,000trmk_TotalEstimatedFairValue    
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (47,362,000)trmk_GrossUnrealizedLossesLessThan12Months (2,663,000)trmk_GrossUnrealizedLossesLessThan12Months (47,362,000)trmk_GrossUnrealizedLossesLessThan12Months    
Gross unrealized (losses), 12 months or more (426,000)trmk_GrossUnrealizedLosses12MonthsOrMore (11,909,000)trmk_GrossUnrealizedLosses12MonthsOrMore (426,000)trmk_GrossUnrealizedLosses12MonthsOrMore    
Total gross unrealized (losses) (47,788,000)trmk_TotalGrossUnrealizedLosses (14,572,000)trmk_TotalGrossUnrealizedLosses (47,788,000)trmk_TotalGrossUnrealizedLosses    
Gains (losses) on investments [Abstract]          
Gross realized (losses)   300,000us-gaap_GainLossOnSaleOfSecuritiesNet 485,000us-gaap_GainLossOnSaleOfSecuritiesNet 1,059,000us-gaap_GainLossOnSaleOfSecuritiesNet  
Pledged to collateralize public deposits and securities sold under repurchase agreements and for other purposes as permitted by law 2,475,000,000trmk_PledgedCollateralizeDepositsAndSecuritiesSoldUnderRepurchaseAgreements 2,457,000,000trmk_PledgedCollateralizeDepositsAndSecuritiesSoldUnderRepurchaseAgreements 2,475,000,000trmk_PledgedCollateralizeDepositsAndSecuritiesSoldUnderRepurchaseAgreements    
Pledged securities providing additional contingency funding   6,000,000trmk_PledgedSecuritiesProvidingAdditionalContingencyFunding      
Available for Sale, amortized cost [Abstract]          
Due in one year or less   18,088,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost      
Due after one year through five years   137,976,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost      
Due after five years through ten years   61,738,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsAmortizedCost      
Due after ten years   82,588,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsAmortizedCost      
Total amortized cost, before mortgage-backed-securities   300,390,000trmk_TotalAmortizedCostBeforeMortgageBackedSecurities      
Mortgage-backed securities   2,051,623,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateAmortizedCost      
Securities available for sale (at amortized cost)   2,352,013,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAmortizedCost      
Available for Sale, estimated fair value [Abstract]          
Due in one year or less   18,236,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue      
Due after one year through five years   142,016,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue      
Due after five years through ten years   63,811,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue      
Due after ten years   82,469,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterTenYearsFairValue      
Total fair value, before mortgage-backed-securities   306,532,000trmk_TotalFairValueOfAvailableForSaleSecuritiesBeforeMortgageBackSecurities      
Mortgage-backed securities   2,068,035,000us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue      
Securities available for sale (at fair value) 2,194,154,000us-gaap_AvailableForSaleSecurities 2,374,567,000us-gaap_AvailableForSaleSecurities 2,194,154,000us-gaap_AvailableForSaleSecurities    
Held to maturity, amortized cost [Abstract]          
Due in one year or less   2,496,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount      
Due after one year through five years   11,693,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsNetCarryingAmount      
Due after five years through ten years   137,991,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsNetCarryingAmount      
Due after ten years   12,296,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsNetCarryingAmount      
Total amortized cost, before mortgage-backed-securities   164,476,000trmk_TotalAmortizedCostHeldToMaturityBeforeMortgageBackedSecurities      
Mortgage-backed securities   1,006,209,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateNetCarryingAmount      
Securities held to maturity (at amortized cost) 1,168,728,000us-gaap_HeldToMaturitySecurities 1,170,685,000us-gaap_HeldToMaturitySecurities 1,168,728,000us-gaap_HeldToMaturitySecurities    
Held to maturity, estimated fair value [Abstract]          
Due in one year or less   2,513,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue      
Due after one year through five years   12,298,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue      
Due after five years through ten years   142,604,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterFiveThroughTenYearsFairValue      
Due after ten years   13,090,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesAfterTenYearsFairValue      
Total fair value, before mortgage-backed-securities   170,505,000trmk_TotalFairValueOfHeldToMaturitySecuritiesBeforeMortgageBackSecurities      
Mortgage-backed securities   1,012,341,000us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithoutSingleMaturityDateFairValue      
Securities held to maturity (at fair value) 1,150,833,000us-gaap_HeldToMaturitySecuritiesFairValue 1,182,846,000us-gaap_HeldToMaturitySecuritiesFairValue 1,150,833,000us-gaap_HeldToMaturitySecuritiesFairValue    
Reclassification of Securities available for sale to securities held to maturity 1,099,000,000trmk_ReclassificationOfAvailableForSaleToHeldToMaturitySecurities        
Net unrealized holding loss on AFS Securities at date of transfer 46,600,000trmk_OtherComprehensiveIncomeLossUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodBeforeTaxAtDateOfTransfer        
Net unrealized holding loss on AFS Securities, net of tax at date of transfer 28,800,000trmk_OtherComprehensiveIncomeLossUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTaxAtDateOfTransfer        
Net unamortized, unrealized loss on transfer of securities   40,400,000trmk_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustment      
Net unamortized, unrealized loss on transfer of securities, net of tax   24,900,000us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax      
Other-than-temporary impairments   0us-gaap_ImpairmentOfInvestments 0us-gaap_ImpairmentOfInvestments 0us-gaap_ImpairmentOfInvestments  
Available-for-sale Securities [Member]          
Gains (losses) on investments [Abstract]          
Proceeds from calls and sales of securities   56,815,000trmk_ProceedsFromCallsAndSalesOfSecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
224,853,000trmk_ProceedsFromCallsAndSalesOfSecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
38,364,000trmk_ProceedsFromCallsAndSalesOfSecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
 
Gross realized gains   456,000trmk_ProceedsFromMaturitiesCallsOfHeldToMaturitySecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
1,680,000trmk_ProceedsFromMaturitiesCallsOfHeldToMaturitySecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
1,052,000trmk_ProceedsFromMaturitiesCallsOfHeldToMaturitySecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
 
Gross realized (losses)   (156,000)us-gaap_GainLossOnSaleOfSecuritiesNet
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
(1,195,000)us-gaap_GainLossOnSaleOfSecuritiesNet
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
(2,000)us-gaap_GainLossOnSaleOfSecuritiesNet
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_AvailableforsaleSecuritiesMember
 
Held-to-maturity Securities [Member]          
Gains (losses) on investments [Abstract]          
Proceeds from calls and sales of securities   0trmk_ProceedsFromCallsAndSalesOfSecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_HeldtomaturitySecuritiesMember
0trmk_ProceedsFromCallsAndSalesOfSecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_HeldtomaturitySecuritiesMember
335,000trmk_ProceedsFromCallsAndSalesOfSecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_HeldtomaturitySecuritiesMember
 
Gross realized gains   0trmk_ProceedsFromMaturitiesCallsOfHeldToMaturitySecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_HeldtomaturitySecuritiesMember
0trmk_ProceedsFromMaturitiesCallsOfHeldToMaturitySecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_HeldtomaturitySecuritiesMember
9,000trmk_ProceedsFromMaturitiesCallsOfHeldToMaturitySecurities
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_HeldtomaturitySecuritiesMember
 
U.S. Government Agency Obligations Issued by U.S. Government Agencies [Member]          
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months 68,908,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
19,220,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
68,908,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
Estimated fair value, 12 months or more 0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
32,656,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
Total estimated fair value 68,908,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
51,876,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
68,908,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (1,485,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(115,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(1,485,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
Gross unrealized (losses), 12 months or more 0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(711,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
Total gross unrealized (losses) (1,485,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(826,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
(1,485,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 0us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
0us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
0us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 0us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
0us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
0us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentAgenciesDebtSecuritiesMember
   
U.S. Government Agency Obligations Issued by U.S. Government Sponsored Agencies [Member]          
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months 138,478,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
9,948,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
138,478,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Estimated fair value, 12 months or more 0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
9,956,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Total estimated fair value 138,478,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
19,904,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
138,478,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (2,101,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
(52,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
(2,101,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Gross unrealized (losses), 12 months or more 0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
(25,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Total gross unrealized (losses) (2,101,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
(77,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
(2,101,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 100,159,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
100,971,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
100,159,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 98,579,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
103,602,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
98,579,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember
   
Obligations of States and Political Subdivisions [Member]          
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months 55,963,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
8,431,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
55,963,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Estimated fair value, 12 months or more 796,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
3,800,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
796,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Total estimated fair value 56,759,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
12,231,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
56,759,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (586,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(22,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(586,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Gross unrealized (losses), 12 months or more (10,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(46,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(10,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Total gross unrealized (losses) (596,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(68,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
(596,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 65,987,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
63,505,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
65,987,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 68,512,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
66,903,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
68,512,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
   
Residential Mortgage Pass-Through Securities Guaranteed by GNMA [Member]          
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months 14,732,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
7,199,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
14,732,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Estimated fair value, 12 months or more 161,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
647,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
161,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Total estimated fair value 14,893,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
7,846,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
14,893,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (155,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
(22,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
(155,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Gross unrealized (losses), 12 months or more (1,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
(8,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
(1,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Total gross unrealized (losses) (156,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
(30,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
(156,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 9,433,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
19,115,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
9,433,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 9,503,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
19,565,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
9,503,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesGuaranteedByGnmaMember
   
Residential Mortgage Pass-Through Securities Issued by FNMA and FHLMC [Member]          
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months 118,466,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
  118,466,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Estimated fair value, 12 months or more 0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
  0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Total estimated fair value 118,466,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
  118,466,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (2,071,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
  (2,071,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Gross unrealized (losses), 12 months or more 0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
  0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Total gross unrealized (losses) (2,071,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
  (2,071,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 12,724,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
11,437,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
12,724,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 12,592,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
11,908,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
12,592,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_ResidentialMortgagePassThroughSecuritiesIssuedByFnmaAndFhlmcMember
   
Other Residential Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]          
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months 1,534,381,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
537,033,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
1,534,381,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Estimated fair value, 12 months or more 23,458,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
395,342,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
23,458,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Total estimated fair value 1,557,839,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
932,375,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
1,557,839,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (36,750,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
(2,449,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
(36,750,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Gross unrealized (losses), 12 months or more (415,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
(10,031,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
(415,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Total gross unrealized (losses) (37,165,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
(12,480,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
(37,165,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 837,393,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
834,176,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
837,393,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 822,321,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
838,700,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
822,321,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= trmk_OtherResidentialMortgageBackedSecuritiesIssuedOrGuaranteedByFnmaFhlmcOrGnmaMember
   
Commercial Mortgage-Backed Securities Issued or Guaranteed by FNMA, FHLMC or GNMA [Member]          
Estimated fair value [Abstract]          
Estimated fair value, less than 12 months 177,412,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
9,134,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
177,412,000trmk_EstimatedFairValueLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Estimated fair value, 12 months or more 0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
79,829,000trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
0trmk_EstimatedFairValue12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Total estimated fair value 177,412,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
88,963,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
177,412,000trmk_TotalEstimatedFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Gross unrealized losses [Abstract]          
Gross unrealized (losses), less than 12 months (4,214,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
(3,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
(4,214,000)trmk_GrossUnrealizedLossesLessThan12Months
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Gross unrealized (losses), 12 months or more 0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
(1,088,000)trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
0trmk_GrossUnrealizedLosses12MonthsOrMore
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Total gross unrealized (losses) (4,214,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
(1,091,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
(4,214,000)trmk_TotalGrossUnrealizedLosses
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 143,032,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
141,481,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
143,032,000us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 139,326,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
142,168,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
139,326,000us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_CommercialMortgageBackedSecuritiesMember
   
Asset-Backed Securities and Structured Financial Products [Member]          
Held to maturity, amortized cost [Abstract]          
Securities held to maturity (at amortized cost) 0us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_AssetBackedSecuritiesMember
0us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_AssetBackedSecuritiesMember
0us-gaap_HeldToMaturitySecurities
/ us-gaap_DebtSecurityAxis
= us-gaap_AssetBackedSecuritiesMember
   
Held to maturity, estimated fair value [Abstract]          
Securities held to maturity (at fair value) 0us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_AssetBackedSecuritiesMember
0us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_AssetBackedSecuritiesMember
0us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_AssetBackedSecuritiesMember
   
Collateralized Loan Obligations [Member]          
Gross unrealized losses [Abstract]          
Sale of collateralized loan obligations 135,600,000us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedLoanObligationsMember
       
Net gain on sale of collateralized loan obligations 1,300,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedLoanObligationsMember
      389,000us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedLoanObligationsMember
Collateralized loan obligations sold during the first quarter of 2014         $ 25,900,000trmk_AvailableForSaleSecuritiesDebtSecuritiesSold
/ us-gaap_DebtSecurityAxis
= us-gaap_CollateralizedLoanObligationsMember