LHFI and Allowance for Loan Losses, LHFI - Troubled Debt Restructuring Related to Loans Held for Investment, Excluding Covered Loans, by Loan Type (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable Modifications [Line Items]
Nonaccrual	$ 49,234	$ 55,312
Construction, Land Development and Other Land [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	3,323	6,123
Secured by 1-4 Family Residential Properties [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	20,329	23,079
Secured by Nonfarm, Nonresidential Properties [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	8,482	17,800
Other Real Estate Secured [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	402	145
Commercial and Industrial Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	15,824	7,622
Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Nonaccrual	300	31
Troubled Debt Restructurings [Member]
Financing Receivable Modifications [Line Items]
Accruing	53	2,235	$ 1,385
Nonaccrual	14,427	7,418	9,910
Total	14,480	9,653	11,295
Troubled Debt Restructurings [Member] \| Construction, Land Development and Other Land [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	0	0	0
Nonaccrual	405	869	3,665
Total	405	869	3,665
Troubled Debt Restructurings [Member] \| Secured by 1-4 Family Residential Properties [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	0	1,426	1,385
Nonaccrual	2,873	2,424	3,733
Total	2,873	3,850	5,118
Troubled Debt Restructurings [Member] \| Secured by Nonfarm, Nonresidential Properties [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing	0	809	0
Nonaccrual	881	3,662	1,854
Total	881	4,471	1,854
Troubled Debt Restructurings [Member] \| Other Real Estate Secured [Member] \| Loans Secured by Real Estate [Member]
Financing Receivable Modifications [Line Items]
Accruing			0
Nonaccrual			149
Total			149
Troubled Debt Restructurings [Member] \| Commercial and Industrial Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	53	0	0
Nonaccrual	10,266	463	509
Total	10,319	$ 463	$ 509
Troubled Debt Restructurings [Member] \| Consumer Loans [Member]
Financing Receivable Modifications [Line Items]
Accruing	0
Nonaccrual	2
Total	$ 2

Recorded investment in TDR's that are still accruing.

No definition available.

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

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=d3e5111-111524

+ Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=trmk_ConstructionLandDevelopmentAndOtherFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CollateralAxis=us-gaap_RealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=trmk_ResidentialFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=trmk_NonresidentialPropertiesFinancingReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=trmk_OtherRealEstateSecuredFinancingReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LoanRestructuringModificationAxis=trmk_TroubledDebtRestructuringsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: