Name:	trmk_AssumedAveragePrepaymentSpeed
Namespace Prefix:	trmk_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

Mortgage loan servicing Ppack expenses.

No definition available.

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

The period of time the company is required to provide a response to putback requests.

No definition available.

Name:	trmk_PeriodOfPutbackResponse
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Schedule of changes in the reserve for mortgage loan [Abstract]

No definition available.

Name:	trmk_ScheduleOfChangesInTheReserveForMortgageLoanServicingPutbackExpenseAbstract
Namespace Prefix:	trmk_
Data Type:	xbrli:stringItemType
Balance Type:	na
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The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(13)(h))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Name:	us-gaap_GainLossOnSalesOfLoansNet
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Amount of decrease in investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from sale.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478322/948-310-S50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G)(Footnote 6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

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

Amount of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, written down.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478322/948-310-S50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 948
-SubTopic 310
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29(Column G)(Footnote 7))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1

Name:	us-gaap_MortgageLoansOnRealEstateWritedownOrReserveAmount1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

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

Discount rate used to estimate the fair value of servicing assets and servicing liabilities.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-2