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Stock and Incentive Compensation Plans (Details) (USD $) In Thousands, except Share data, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Options [Roll Forward] |  |  |
Outstanding, beginning of year (in shares) | 105,450 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 699,600 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 1,205,100 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Exercised (in shares) | 0 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised | (187,300)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised | (11,125)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised
Expired (in shares) | (105,450)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod | (406,850)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod | (494,375)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod
Outstanding, end of year (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 105,450 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber | 699,600 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
Exercisable, end of year (in shares) | 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber | 105,450 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber | 699,600 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber
Average Option Price [Abstract] |  |  |
Outstanding, beginning of year (in dollars per share) | $ 27.43 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 27.58 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 27.31 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Exercised (in dollars per share) | $ 0 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice | $ 26.96 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice | $ 24.09 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice
Expired (in dollars per share) | $ 27.43 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice | $ 27.90 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice | $ 27.01 us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice
Outstanding, end of year (in dollars per share) | $ 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 27.43 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice | $ 27.58 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice
Exercisable, end of year (in dollars per share) | $ 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice | $ 27.43 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice | $ 27.58 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice
Compensation expense for all stock incentive plans [Abstract] |  |  |
Recognized compensation expense | $ 4,152 us-gaap_AllocatedShareBasedCompensationExpense | $ 3,599 us-gaap_AllocatedShareBasedCompensationExpense | $ 3,973 us-gaap_AllocatedShareBasedCompensationExpense
Unrecognized compensation expense | 4,816 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized |  |
Performance Based Award [Member] |  |  |
Shares [Roll Forward] |  |  |
Nonvested shares, beginning of year (in shares) | 160,520 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 159,583 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 179,421 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Granted (in shares) | 73,726 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 62,119 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 55,295 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Released from restriction (in shares) | (38,580)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | (54,784)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | (72,632)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Forfeited (in shares) | (14,471)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | (6,398)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | (2,501)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Nonvested shares, end of year (in shares) | 181,195 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 160,520 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 159,583 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Weighted-Average Grant Date Fair Value [Abstract] |  |  |
Nonvested shares, beginning of year (in dollars per share) | $ 25.20 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 24.26 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 20.30 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Granted (in dollars per share) | $ 25.58 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 23.65 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 25.66 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Released from restriction (in dollars per share) | $ 25.40 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 24.15 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 21.38 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Forfeited (in dollars per share) | $ 24.86 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 25.42 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 24.70 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Nonvested shares, end of year (in dollars per share) | $ 24.98 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 25.20 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | $ 24.26 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Compensation expense for all stock incentive plans [Abstract] |  |  |
Recognized compensation expense | 1,065 us-gaap_AllocatedShareBasedCompensationExpense / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 825 us-gaap_AllocatedShareBasedCompensationExpense / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember | 868 us-gaap_AllocatedShareBasedCompensationExpense / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember
Unrecognized compensation expense | 1,197 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_PerformanceBasedAwardMember |  |
Weighted average life of unrecognized compensation expense | 1 year 8 months 23 days |  |
Performance Awards Includes Achievement Shares for Grants after 2013 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Vesting period | 3 years |  |
Achievement Shares from Performance Grants Prior to 2013 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Vesting period | 3 years |  |
Time-vested Awards [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Vesting period | 3 years |  |
Shares [Roll Forward] |  |  |
Nonvested shares, beginning of year (in shares) | 291,634 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 317,573 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 334,356 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Granted (in shares) | 105,690 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 112,964 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 141,616 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Released from restriction (in shares) | (124,869)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | (122,727)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | (151,331)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Forfeited (in shares) | (8,550)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | (16,176)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | (7,068)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Nonvested shares, end of year (in shares) | 263,905 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 291,634 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 317,573 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Weighted-Average Grant Date Fair Value [Abstract] |  |  |
Nonvested shares, beginning of year (in dollars per share) | $ 24.48 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 23.28 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 21.04 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Granted (in dollars per share) | $ 24.91 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 24.47 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 24.66 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Released from restriction (in dollars per share) | $ 24.74 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 24.40 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 23.14 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Forfeited (in dollars per share) | $ 24.77 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 25.14 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 24.14 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Nonvested shares, end of year (in dollars per share) | $ 24.66 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 24.48 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | $ 23.28 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Compensation expense for all stock incentive plans [Abstract] |  |  |
Recognized compensation expense | 3,087 us-gaap_AllocatedShareBasedCompensationExpense / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 2,774 us-gaap_AllocatedShareBasedCompensationExpense / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember | 3,105 us-gaap_AllocatedShareBasedCompensationExpense / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember
Unrecognized compensation expense | 3,619 us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized / trmk_ScheduleOfShareBasedCompensationArrangementByAwardBasisAxis = trmk_TimeVestedAwardMember |  |
Weighted average life of unrecognized compensation expense | 1 year 9 months 4 days |  |
Restricted Stock Units (RSUs) [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
ROATE Performance measure (in hundredths) | 100.00%trmk_RoateLevelPerformanceMeasures / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |
TSR Performance measure (in hundredths) | 100.00%trmk_TsrPerformanceMeasure / us-gaap_AwardTypeAxis = us-gaap_RestrictedStockUnitsRSUMember |  |
Stock Option-based Awards [Member] |  |  |
Average Option Price [Abstract] |  |  |
Total intrinsic value of options exercised | $ 0 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 191 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember | $ 16 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue / us-gaap_AwardTypeAxis = us-gaap_EmployeeStockOptionMember
1997 Long Term Incentive Plan [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Vesting period | 4 years |  |
Stock and incentive compensation plan, contractual term | 10 years |  |
2005 Stock and Incentive Compensation Plan [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Common stock available for issuance (in shares) | 5,466,172 us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant / trmk_ScheduleOfShareBasedCompensationArrangementByShareBasedPaymentPlanNameAxis = trmk_StockAndIncentiveCompensationPlan2005Member |  |
Vesting period | 5 years |  |
Stock and incentive compensation plan, contractual term | 7 years |  |

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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(3) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(iv)(4) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Number of options outstanding, including both vested and non-vested options. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i)-(ii) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1)(i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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