Fair Value - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Fair Value Disclosures [Abstract]
Outstanding balances in collateral dependent related to allowance for credit losses	$ 39,900		$ 40,300
Collateral dependent related to allowance for credit losses	17,900		17,700
Foreclosed assets remeasured after initial recognition	430
Write-downs of allowance for foreclosed assets after initial recognition	20	$ 0
Noninterest gain (loss) Mortgage banking, net for changes in fair value of LHFS	944	(5,600)
Interest earned on LHFS included in Interest and fees on LHFS and LHFI	1,500	$ 1,300
Serviced GNMA loans eligible for repurchase	$ (55,400)		$ (70,800)

Financing receivable where repayment is expected to be provided substantially through the sale of the collateral.

No definition available.

Name:	trmk_CollateralDependentFinancingReceivable
Namespace Prefix:	trmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Allowance for credit losses on financing receivable where repayment is expected to be provided substantially through the sale of the collateral.

+ References

No definition available.

+ Details

Name:	trmk_CollateralDependentFinancingReceivableAllowanceForCreditLosses
Namespace Prefix:	trmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The (re)measured fair value amount, as of the balance sheet date, of all assets obtained in full or partial satisfaction of a debt arrangement through foreclosure proceedings or defeasance; includes real and personal property; equity interests in corporations, partnerships, and joint ventures; and beneficial interests in trusts.

+ References

No definition available.

+ Details

Name:	trmk_ForeclosedAssetsRemeasuredAfterInitialRecognitionFairValue
Namespace Prefix:	trmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Refers to interest and fees derived on loans held for sale.

+ References

No definition available.

+ Details

Name:	trmk_InterestAndFeesOnLHFSAndLHFI
Namespace Prefix:	trmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Loans available for repurchase.

+ References

No definition available.

+ Details

Name:	trmk_LoansAvailableForRepurchase
Namespace Prefix:	trmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The overvalued amount that is written down to reduce the carrying value of an asset, that was valued at initial recognition of foreclosure, to the fair value.

+ References

No definition available.

+ Details

Name:	trmk_WriteDownOfAllowanceAfterInitialRecognitionOfForeclosure
Namespace Prefix:	trmk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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

- Definition

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI https://asc.fasb.org/extlink&oid=123596393&loc=d3e14172-108612

+ Details

Name:	us-gaap_FairValueOptionChangesInFairValueGainLoss1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration