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Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI (5) (Details) (USD $) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | $ 15,146,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue |  | $ 12,606,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue |
Past Due 60 - 89 Days | 3,145,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue |  | 2,839,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue |
Past Due Greater Than 90 Days | 2,764,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing | [1] | 3,298,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing | [1]
Total Past Due | 21,055,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue |  | 18,743,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue |
Nonaccrual | 79,343,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus |  | 65,238,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus |
Current Loans | 6,349,071,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent |  | 5,714,900,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent |
Total LHFI | 6,449,469,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |  | 5,798,881,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome |
LHFI past due 90 days or more | 2,800,000 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue |  | 3,300,000 us-gaap_FinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue |
LHFS past due 90 days or more | 25,900,000 trmk_CoveredServicedFinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue |  | 21,500,000 trmk_CoveredServicedFinancingReceivableRecordedInvestmentEqualToGreaterThan90DaysPastDue |
Percentage of outstanding principal to be repurchased under GNMA optional repurchase program (in hundredths) | 100.00%trmk_OptionalRepurchaseProgramPrincipalPercentageToBeRepurchased |  |  |
Amount of delinquent loans repurchased |  |  | 57,400,000 trmk_FinancingReceivableDelinquentRecordedInvestmentRepurchased |
Repurchase gain included in gain on sales of loans |  |  | 534,000 trmk_GainLossOnRepurchaseOfDebtInstrumentIncludedInGainOnSalesOfLoans |
Loans Secured by Real Estate [Member] | Construction, Land Development and Other Land [Member] |  |  |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | 248,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 656,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due 60 - 89 Days | 17,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 267,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due Greater Than 90 Days | 60,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1] | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1]
Total Past Due | 325,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 923,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Nonaccrual | 13,867,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 13,327,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Current Loans | 605,685,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 582,639,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI | 619,877,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 596,889,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Loans Secured by Real Estate [Member] | Secured by 1-4 Family Residential Properties [Member] |  |  |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | 8,424,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 7,322,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due 60 - 89 Days | 2,428,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 2,115,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due Greater Than 90 Days | 2,367,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1] | 2,996,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1]
Total Past Due | 13,219,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 12,433,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Nonaccrual | 25,621,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 21,603,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Current Loans | 1,595,557,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 1,451,528,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI | 1,634,397,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 1,485,564,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_ResidentialFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Loans Secured by Real Estate [Member] | Nonfarm, Nonresidential Properties [Member] |  |  |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | 1,960,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 1,934,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due 60 - 89 Days | 34,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 110,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due Greater Than 90 Days | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1] | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1]
Total Past Due | 1,994,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 2,044,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Nonaccrual | 25,717,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 21,809,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Current Loans | 1,525,482,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 1,391,286,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI | 1,553,193,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 1,415,139,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_NonresidentialPropertiesFinancingReceivablesMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Loans Secured by Real Estate [Member] | Other Real Estate Secured Financing Receivable [Member] |  |  |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | 80,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 2,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due 60 - 89 Days | 0 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 3,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Past Due Greater Than 90 Days | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1] | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember | [1]
Total Past Due | 80,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 5,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Nonaccrual | 1,318,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 1,327,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Current Loans | 252,389,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 188,030,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Total LHFI | 253,787,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |  | 189,362,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / trmk_FinancingReceivableBySubClassReceivableAxis = trmk_OtherRealEstateSecuredFinancingReceivableMember / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_RealEstateSecuredFinancingReceivableMember |
Commercial And Industrial Loans [Member] |  |  |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | 2,491,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |  | 809,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |
Past Due 60 - 89 Days | 306,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |  | 198,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |
Past Due Greater Than 90 Days | 126,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember | [1] | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember | [1]
Total Past Due | 2,923,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |  | 1,007,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |
Nonaccrual | 12,104,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |  | 6,286,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |
Current Loans | 1,255,323,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |  | 1,150,321,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |
Total LHFI | 1,270,350,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |  | 1,157,614,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_CommercialAndIndustrialLoansMember |
Consumer Loans [Member] |  |  |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | 1,811,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |  | 1,866,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Past Due 60 - 89 Days | 351,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |  | 146,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Past Due Greater Than 90 Days | 211,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | [1] | 302,000 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember | [1]
Total Past Due | 2,373,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |  | 2,314,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Nonaccrual | 88,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |  | 151,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Current Loans | 165,503,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |  | 162,843,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Total LHFI | 167,964,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |  | 165,308,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_ConsumerLoansFinancingReceivableMember |
Other Loans [Member] |  |  |  |
Financing Receivable, Recorded Investment, Aging [Abstract] |  |  |  |
Past Due 30 - 59 Days | 132,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |  | 17,000 us-gaap_FinancingReceivableRecordedInvestment30To59DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Past Due 60 - 89 Days | 9,000 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |  | 0 us-gaap_FinancingReceivableRecordedInvestment60To89DaysPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Past Due Greater Than 90 Days | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | [1] | 0 us-gaap_FinancingReceivableRecordedInvestment90DaysPastDueAndStillAccruing / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember | [1]
Total Past Due | 141,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |  | 17,000 us-gaap_FinancingReceivableRecordedInvestmentPastDue / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Nonaccrual | 628,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |  | 735,000 us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Current Loans | 949,132,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |  | 788,253,000 us-gaap_FinancingReceivableRecordedInvestmentCurrent / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
Total LHFI | $ 949,901,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |  | $ 789,005,000 us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = trmk_OtherLoansFinancingReceivableMember |
[1] | Past due 90 days or more but still accruing interest.

X
- Definition Covered serviced financing receivables eligible for repurchase that are equal to or greater than 90 days past due. + References No definition available. + Details
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Namespace Prefix: | trmk_
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X
- Definition Delinquent recorded investment in financing receivables that were repurchased during the period. + References No definition available. + Details
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Balance Type: | debit
Period Type: | duration

X
- Definition Amount of gain (loss) from repurchase price of a debt instrument initially issued by the entity and then exercised by option included in gain on sales of loans. + References No definition available. + Details
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Balance Type: | credit
Period Type: | duration

X
- Definition The amount of the outstanding principal of a loan to be repurchased under GNMA Optional repurchase Program for loans in a pool that become delinquent. + References No definition available. + Details
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Namespace Prefix: | trmk_
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Period Type: | duration

X
- Definition Financing receivables that are less than 60 days past due but more than 29 days past due. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524 + Details
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Period Type: | instant

X
- Definition Financing receivables that are less than 90 days past due but more than 59 days past due. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524 + Details
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Balance Type: | debit
Period Type: | instant

X
- Definition Recorded investment in financing receivables that are 90 days or more past due and still accruing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524 + Details
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X
- Details
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Balance Type: | na
Period Type: | duration

X
- Definition Financing receivables that are current. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524 + Details
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Balance Type: | debit
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X
- Definition Financing receivables that are equal to or greater than 90 days past due. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524 + Details
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Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524 + Details
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Balance Type: | debit
Period Type: | instant

X
- Definition Recorded Investment in financing receivables that are past due at the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7A -URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524 + Details
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X
- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5074-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522 + Details
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Balance Type: | debit
Period Type: | instant

X
- Details
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Namespace Prefix: |
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- Details
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- Details
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- Details
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