Acquired Loans - Additional Information (Details)	9 Months Ended
Sep. 30, 2019 CreditRiskGrade
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities [Abstract]
Number of individual credit risk grades	10

This line item represents the number of individual credit risk grades established by the entity.

No definition available.

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