Contingencies (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Loss Contingencies [Line Items]
Unused commitments to extend credit	$ 2,583us-gaap_UnusedCommitmentsToExtendCredit	$ 2,289us-gaap_UnusedCommitmentsToExtendCredit
Standby Letters of Credit [Member]
Loss Contingencies [Line Items]
Maximum potential exposure to credit loss in the event of nonperformance	131.7	147.2
Letters of credit, maturity term - maximum	3 years
Collateral held, fair value	29.6
Pending or Threatened Litigation, Stanford Financial Group [Member]
Legal Proceedings [Abstract]
Lawsuits naming entity as defendant, number	2
Pending or Threatened Litigation, Overdraft Fees [Member]
Legal Proceedings [Abstract]
Lawsuits naming entity as defendant, number	2
Litigation settlement	4.0
Litigation settlement net of taxes	$ 2.5
Potential claims resolved by settlement	100,000
Number of customers that excluded themselves from the class action settlement	16

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The maximum maturity (in years) of outstanding letters of credit issued by company.

+ References

No definition available.

+ Details

Name:	trmk_LettersOfCreditMaximumMaturity
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- Definition

Amount of litigation expense, net of taxes, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

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

- Definition

Refers to the number of customers who excluded themselves from the class action settlement.

+ References

No definition available.

+ Details

Name:	trmk_NumberOfCustomersThatExcludedThemselvesFromClassActionSettlement
Namespace Prefix:	trmk_
Data Type:	xbrli:integerItemType
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Period Type:	instant

- Definition

Refers to number of class members whose potential claims were resolved by settlement.

+ References

No definition available.

+ Details

Name:	trmk_PotentialClaimsResolvedBySettlement
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- Definition

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_LossContingenciesLineItems
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- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
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- Definition

The estimated maximum amount of possible loss from the contingency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 20

-Section 50

-Paragraph 9

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

+ Details

Name:	us-gaap_LossContingencyRangeOfPossibleLossMaximum
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Data Type:	xbrli:monetaryItemType
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- Definition

The carrying amount (fair value) as of the balance sheet date of securities held that had been pledged by counterparties under financing and lending arrangements, pursuant to which the entity has the right by agreement or custom to sell or re-pledge such securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5086-111524

+ Details

Name:	us-gaap_SecuritiesHeldAsCollateralAtFairValue
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Unused amount of commitments to extend credit to customers.

+ References

No definition available.

+ Details

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

- Details

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- Details

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- Details

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