LHFI and Allowance for Loan Losses, LHFI - Additional Information (Details 3)	12 Months Ended
Dec. 31, 2018 Factor Loan Scale
Financing Receivable, Allowance for Credit Loss, Additional Information [Abstract]
Number of loan types for commercial portfolio \| Loan	9
Number of risk rate factors for commercial loans \| Factor	450
Minimum score for qualitative risk factor \| Scale	0
Maximum score for qualitative risk factor \| Scale	100
Number of unique qualitative factors used to analyze consumer loans \| Factor	5
Number of loan types for consumer portfolio \| Loan	5

The number of unique loan types the commercial portfolio was delineated into for analysis of loan loss allowance.

No definition available.

Name:	trmk_NumberOfLoanTypesForCommercialPortfolio
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of unique loan types the consumer portfolio was delineated into for analysis of loan loss allowance.

No definition available.

Name:	trmk_NumberOfLoanTypesForConsumerPortfolio
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of risk rate factors utilized for the commercial portfolio.

No definition available.

Name:	trmk_NumberOfRiskRateTypesForCommercialPortfolio
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

The number of unique qualitative factors used to evaluate the consumer loan portfolio for loan loss allowance.

No definition available.

Name:	trmk_NumberOfUniqueQualitativeFactorsUsedToAnalyzeConsumerLoans
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

When presenting a range of scores, the highest potential score under the assessment procedure.

No definition available.

Name:	trmk_QualitativeRiskFactorScoreRangeMaximum
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

When presenting a range of scores, the lowest potential score under the assessment procedure.

No definition available.

Name:	trmk_QualitativeRiskFactorScoreRangeMinimum
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

No definition available.

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossAdditionalInformationAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration